TGraph Class Reference

A TGraph is an object made of two arrays X and Y with npoints each.

The TGraph painting is performed thanks to the TGraphPainter class. All details about the various painting options are given in this class.

Notes

• Unlike histogram or tree (or even TGraph2D), TGraph objects are not automatically attached to the current TFile, in order to keep the management and size of the TGraph as small as possible.
• The TGraph constructors do not have the TGraph title and name as parameters. A TGraph has the default title and name "Graph". To change the default title and name SetTitle and SetName should be called on the TGraph after its creation. TGraph was a light weight object to start with, like TPolyline or TPolyMarker. That’s why it did not have any title and name parameters in the constructors.

Example

The picture below gives an example:

{
   double x[100], y[100];
   int n = 20;
   for (int i=0;i<n;i++) {
     x[i] = i*0.1;
     y[i] = 10*sin(x[i]+0.2);
   }
   auto g = new TGraph(n,x,y);
   g->SetTitle("Graph title;X title;Y title");
   g->Draw("AC*");
}

Default X-Points

If one doesn't specify the points in the x-axis, they will get the default values 0, 1, 2, 3, (etc. depending on the length of the y-points):

{
   double y[6] = {3, 8, 1, 10, 5, 7};
   auto g = new TGraph(6,y);
   g->SetTitle("A Graph with default X points");
   g->Draw();
}

Definition at line 41 of file TGraph.h.

Public Types
enum	EStatusBits {   kNoStats = (1ULL << ( 9 )) , kClipFrame = (1ULL << ( 10 )) , kResetHisto = (1ULL << ( 17 )) , kNotEditable = (1ULL << ( 18 )) ,   kIsSortedX = (1ULL << ( 19 )) , kIsHighlight = (1ULL << ( 20 )) }
Public Types inherited from TObject
enum	{   kIsOnHeap = 0x01000000 , kNotDeleted = 0x02000000 , kZombie = 0x04000000 , kInconsistent = 0x08000000 ,   kBitMask = 0x00ffffff }
enum	{ kSingleKey = (1ULL << ( 0 )) , kOverwrite = (1ULL << ( 1 )) , kWriteDelete = (1ULL << ( 2 )) }
enum	EDeprecatedStatusBits { kObjInCanvas = (1ULL << ( 3 )) }
enum	EStatusBits {   kCanDelete = (1ULL << ( 0 )) , kMustCleanup = (1ULL << ( 3 )) , kIsReferenced = (1ULL << ( 4 )) , kHasUUID = (1ULL << ( 5 )) ,   kCannotPick = (1ULL << ( 6 )) , kNoContextMenu = (1ULL << ( 8 )) , kInvalidObject = (1ULL << ( 13 )) }

Public Member Functions
	TGraph ()
	Graph default constructor.
	TGraph (const char *filename, const char *format="%lg %lg", Option_t *option="")
	Graph constructor reading input from filename.
	TGraph (const TF1 *f, Option_t *option="")
	Graph constructor importing its parameters from the TF1 object passed as argument.
	TGraph (const TGraph &gr)
	Copy constructor for this graph.
	TGraph (const TH1 *h)
	Graph constructor importing its parameters from the TH1 object passed as argument.
	TGraph (const TVectorD &vx, const TVectorD &vy)
	Graph constructor with two vectors of doubles in input A graph is build with the X coordinates taken from vx and Y coord from vy The number of points in the graph is the minimum of number of points in vx and vy.
	TGraph (const TVectorF &vx, const TVectorF &vy)
	Graph constructor with two vectors of floats in input A graph is build with the X coordinates taken from vx and Y coord from vy The number of points in the graph is the minimum of number of points in vx and vy.
	TGraph (Int_t n)
	Constructor with only the number of points set the arrays x and y will be set later.
	TGraph (Int_t n, const Double_t *x, const Double_t *y)
	Graph normal constructor with doubles.
	TGraph (Int_t n, const Double_t *y, Double_t start=0., Double_t step=1.)
	Default X-Points constructor.
	TGraph (Int_t n, const Float_t *x, const Float_t *y)
	Graph normal constructor with floats.
	TGraph (Int_t n, const Int_t *x, const Int_t *y)
	Graph normal constructor with ints.
	~TGraph () override
	Graph default destructor.
virtual void	AddPoint (Double_t x, Double_t y)
	Append a new point to the graph.
virtual void	Apply (TF1 *f)
	Apply function f to all the data points f may be a 1-D function TF1 or 2-d function TF2 The Y values of the graph are replaced by the new values computed using the function.
void	Browse (TBrowser *b) override
	Browse.
virtual Double_t	Chisquare (TF1 *f1, Option_t *option="") const
	Return the chisquare of this graph with respect to f1.
virtual void	ComputeRange (Double_t &xmin, Double_t &ymin, Double_t &xmax, Double_t &ymax) const
	Compute the x/y range of the points in this graph.
Int_t	DistancetoPrimitive (Int_t px, Int_t py) override
	Compute distance from point px,py to a graph.
void	Draw (Option_t *chopt="") override
	Draw this graph with its current attributes.
virtual void	DrawGraph (Int_t n, const Double_t *x=nullptr, const Double_t *y=nullptr, Option_t *option="")
	Draw this graph with new attributes.
virtual void	DrawGraph (Int_t n, const Float_t *x, const Float_t *y, Option_t *option="")
	Draw this graph with new attributes.
virtual void	DrawGraph (Int_t n, const Int_t *x, const Int_t *y, Option_t *option="")
	Draw this graph with new attributes.
virtual void	DrawPanel ()
	Display a panel with all graph drawing options.
virtual Double_t	Eval (Double_t x, TSpline *spline=nullptr, Option_t *option="") const
	Interpolate points in this graph at x using a TSpline.
void	ExecuteEvent (Int_t event, Int_t px, Int_t py) override
	Execute action corresponding to one event.
virtual void	Expand (Int_t newsize)
	If array sizes <= newsize, expand storage to 2*newsize.
virtual void	Expand (Int_t newsize, Int_t step)
	If graph capacity is less than newsize points then make array sizes equal to least multiple of step to contain newsize points.
TObject *	FindObject (const char *name) const override
	Search object named name in the list of functions.
TObject *	FindObject (const TObject *obj) const override
	Search object obj in the list of functions.
virtual TFitResultPtr	Fit (const char *formula, Option_t *option="", Option_t *goption="", Axis_t xmin=0, Axis_t xmax=0)
	Fit this graph with function with name fname.
virtual TFitResultPtr	Fit (TF1 *f1, Option_t *option="", Option_t *goption="", Axis_t xmin=0, Axis_t xmax=0)
	Fit this graph with function f1.
virtual void	FitPanel ()
	Display a GUI panel with all graph fit options.
virtual Double_t	GetCorrelationFactor () const
	Return graph correlation factor.
virtual Double_t	GetCovariance () const
	Return covariance of vectors x,y.
Bool_t	GetEditable () const
	Return kTRUE if kNotEditable bit is not set, kFALSE otherwise.
virtual Double_t	GetErrorX (Int_t bin) const
	It always returns a negative value. Real implementation in TGraphErrors.
virtual Double_t	GetErrorXhigh (Int_t bin) const
	It always returns a negative value.
virtual Double_t	GetErrorXlow (Int_t bin) const
	It always returns a negative value.
virtual Double_t	GetErrorY (Int_t bin) const
	It always returns a negative value. Real implementation in TGraphErrors.
virtual Double_t	GetErrorYhigh (Int_t bin) const
	It always returns a negative value.
virtual Double_t	GetErrorYlow (Int_t bin) const
	It always returns a negative value.
virtual Double_t *	GetEX () const
virtual Double_t *	GetEXhigh () const
virtual Double_t *	GetEXhighd () const
virtual Double_t *	GetEXlow () const
virtual Double_t *	GetEXlowd () const
virtual Double_t *	GetEY () const
virtual Double_t *	GetEYhigh () const
virtual Double_t *	GetEYhighd () const
virtual Double_t *	GetEYlow () const
virtual Double_t *	GetEYlowd () const
TF1 *	GetFunction (const char *name) const
	Return pointer to function with name.
virtual TH1F *	GetHistogram () const
	Returns a pointer to the histogram used to draw the axis Takes into account the two following cases.
TList *	GetListOfFunctions () const
Double_t	GetMaximum () const
Int_t	GetMaxSize () const
virtual Double_t	GetMean (Int_t axis=1) const
	Return mean value of X (axis=1) or Y (axis=2)
Double_t	GetMinimum () const
Int_t	GetN () const
char *	GetObjectInfo (Int_t px, Int_t py) const override
	Implementation to get information on point of graph at cursor position Adapted from class TH1.
virtual Int_t	GetPoint (Int_t i, Double_t &x, Double_t &y) const
	Get x and y values for point number i.
virtual Double_t	GetPointX (Int_t i) const
	Get x value for point i.
virtual Double_t	GetPointY (Int_t i) const
	Get y value for point i.
virtual Double_t	GetRMS (Int_t axis=1) const
	Return RMS of X (axis=1) or Y (axis=2)
Double_t *	GetX () const
TAxis *	GetXaxis () const
	Get x axis of the graph.
Double_t *	GetY () const
TAxis *	GetYaxis () const
	Get y axis of the graph.
virtual void	InitExpo (Double_t xmin=0, Double_t xmax=0)
	Compute Initial values of parameters for an exponential.
virtual void	InitGaus (Double_t xmin=0, Double_t xmax=0)
	Compute Initial values of parameters for a gaussian.
virtual void	InitPolynom (Double_t xmin=0, Double_t xmax=0)
	Compute Initial values of parameters for a polynom.
virtual Int_t	InsertPoint ()
	Insert a new point at the mouse position.
virtual void	InsertPointBefore (Int_t ipoint, Double_t x, Double_t y)
	Insert a new point with coordinates (x,y) before the point number ipoint.
virtual Double_t	Integral (Int_t first=0, Int_t last=-1) const
	Integrate the TGraph data within a given (index) range.
TClass *	IsA () const override
virtual Bool_t	IsEditable () const
virtual Bool_t	IsHighlight () const
virtual Int_t	IsInside (Double_t x, Double_t y) const
	Return 1 if the point (x,y) is inside the polygon defined by the graph vertices 0 otherwise.
virtual void	LeastSquareFit (Int_t m, Double_t *a, Double_t xmin=0, Double_t xmax=0)
	Least squares polynomial fitting without weights.
virtual void	LeastSquareLinearFit (Int_t n, Double_t &a0, Double_t &a1, Int_t &ifail, Double_t xmin=0, Double_t xmax=0)
	Least square linear fit without weights.
virtual Int_t	Merge (TCollection *list)
	Adds all graphs from the collection to this graph.
virtual void	MovePoints (Double_t dx, Double_t dy, Bool_t logx=kFALSE, Bool_t logy=kFALSE)
	Move all graph points on specified values dx,dy If log argument specified, calculation done in logarithmic scale like: new_value = exp( log(old_value) + delta );.
TGraph &	operator= (const TGraph &)
	Equal operator for this graph.
void	Paint (Option_t *chopt="") override
	Draw this graph with its current attributes.
void	PaintGraph (Int_t npoints, const Double_t *x, const Double_t *y, Option_t *chopt)
	Draw the (x,y) as a graph.
void	PaintGrapHist (Int_t npoints, const Double_t *x, const Double_t *y, Option_t *chopt)
	Draw the (x,y) as a histogram.
virtual void	PaintStats (TF1 *fit)
	Draw the stats.
void	Print (Option_t *chopt="") const override
	Print graph values.
void	RecursiveRemove (TObject *obj) override
	Recursively remove object from the list of functions.
virtual Int_t	RemovePoint ()
	Delete point close to the mouse position Returns index of removed point (or -1 if nothing was changed)
virtual Int_t	RemovePoint (Int_t ipoint)
	Delete point number ipoint Returns index of removed point (or -1 if nothing was changed)
void	SaveAs (const char *filename, Option_t *option="") const override
	Save the graph as .csv, .tsv or .txt.
void	SavePrimitive (std::ostream &out, Option_t *option="") override
	Save primitive as a C++ statement(s) on output stream out.
virtual void	Scale (Double_t c1=1., Option_t *option="y")
	Multiply the values of a TGraph by a constant c1.
virtual void	Set (Int_t n)
	Set number of points in the graph Existing coordinates are preserved New coordinates above fNpoints are preset to 0.
virtual void	SetEditable (Bool_t editable=kTRUE)
	if editable=kFALSE, the graph cannot be modified with the mouse by default a TGraph is editable
virtual void	SetHighlight (Bool_t set=kTRUE)
	Set highlight (enable/disble) mode for the graph by default highlight mode is disable.
virtual void	SetHistogram (TH1F *h)
virtual void	SetMaximum (Double_t maximum=-1111)
	Set the maximum of the graph.
virtual void	SetMinimum (Double_t minimum=-1111)
	Set the minimum of the graph.
void	SetName (const char *name="") override
	Set graph name.
void	SetNameTitle (const char *name="", const char *title="") override
	Set graph name and title.
virtual void	SetPoint (Int_t i, Double_t x, Double_t y)
	Set x and y values for point number i.
virtual void	SetPointX (Int_t i, Double_t x)
	Set x value for point i.
virtual void	SetPointY (Int_t i, Double_t y)
	Set y value for point i.
virtual void	SetStats (Bool_t stats=kTRUE)
	Set statistics option on/off.
void	SetTitle (const char *title="") override
	Change (i.e.
virtual void	Sort (Bool_t(*greater)(const TGraph *, Int_t, Int_t)=&TGraph::CompareX, Bool_t ascending=kTRUE, Int_t low=0, Int_t high=-1111)
	Sorts the points of this TGraph using in-place quicksort (see e.g.
void	Streamer (TBuffer &) override
	Stream an object of class TGraph.
void	StreamerNVirtual (TBuffer &ClassDef_StreamerNVirtual_b)
void	UseCurrentStyle () override
	Set current style settings in this graph This function is called when either TCanvas::UseCurrentStyle or TROOT::ForceStyle have been invoked.
void	Zero (Int_t &k, Double_t AZ, Double_t BZ, Double_t E2, Double_t &X, Double_t &Y, Int_t maxiterations)
	Find zero of a continuous function.
Public Member Functions inherited from TNamed
	TNamed ()
	TNamed (const char *name, const char *title)
	TNamed (const TNamed &named)
	TNamed copy ctor.
	TNamed (const TString &name, const TString &title)
virtual	~TNamed ()
	TNamed destructor.
void	Clear (Option_t *option="") override
	Set name and title to empty strings ("").
TObject *	Clone (const char *newname="") const override
	Make a clone of an object using the Streamer facility.
Int_t	Compare (const TObject *obj) const override
	Compare two TNamed objects.
void	Copy (TObject &named) const override
	Copy this to obj.
virtual void	FillBuffer (char *&buffer)
	Encode TNamed into output buffer.
const char *	GetName () const override
	Returns name of object.
const char *	GetTitle () const override
	Returns title of object.
ULong_t	Hash () const override
	Return hash value for this object.
TClass *	IsA () const override
Bool_t	IsSortable () const override
void	ls (Option_t *option="") const override
	List TNamed name and title.
TNamed &	operator= (const TNamed &rhs)
	TNamed assignment operator.
void	Print (Option_t *option="") const override
	Print TNamed name and title.
virtual Int_t	Sizeof () const
	Return size of the TNamed part of the TObject.
void	Streamer (TBuffer &) override
	Stream an object of class TObject.
void	StreamerNVirtual (TBuffer &ClassDef_StreamerNVirtual_b)
Public Member Functions inherited from TObject
	TObject ()
	TObject constructor.
	TObject (const TObject &object)
	TObject copy ctor.
virtual	~TObject ()
	TObject destructor.
void	AbstractMethod (const char *method) const
	Use this method to implement an "abstract" method that you don't want to leave purely abstract.
virtual void	AppendPad (Option_t *option="")
	Append graphics object to current pad.
ULong_t	CheckedHash ()
	Check and record whether this class has a consistent Hash/RecursiveRemove setup (*) and then return the regular Hash value for this object.
virtual const char *	ClassName () const
	Returns name of class to which the object belongs.
virtual void	Delete (Option_t *option="")
	Delete this object.
virtual void	DrawClass () const
	Draw class inheritance tree of the class to which this object belongs.
virtual TObject *	DrawClone (Option_t *option="") const
	Draw a clone of this object in the current selected pad with: gROOT->SetSelectedPad(c1).
virtual void	Dump () const
	Dump contents of object on stdout.
virtual void	Error (const char *method, const char *msgfmt,...) const
	Issue error message.
virtual void	Execute (const char *method, const char *params, Int_t *error=nullptr)
	Execute method on this object with the given parameter string, e.g.
virtual void	Execute (TMethod *method, TObjArray *params, Int_t *error=nullptr)
	Execute method on this object with parameters stored in the TObjArray.
virtual void	Fatal (const char *method, const char *msgfmt,...) const
	Issue fatal error message.
virtual Option_t *	GetDrawOption () const
	Get option used by the graphics system to draw this object.
virtual const char *	GetIconName () const
	Returns mime type name of object.
virtual Option_t *	GetOption () const
virtual UInt_t	GetUniqueID () const
	Return the unique object id.
virtual Bool_t	HandleTimer (TTimer *timer)
	Execute action in response of a timer timing out.
Bool_t	HasInconsistentHash () const
	Return true is the type of this object is known to have an inconsistent setup for Hash and RecursiveRemove (i.e.
virtual void	Info (const char *method, const char *msgfmt,...) const
	Issue info message.
virtual Bool_t	InheritsFrom (const char *classname) const
	Returns kTRUE if object inherits from class "classname".
virtual Bool_t	InheritsFrom (const TClass *cl) const
	Returns kTRUE if object inherits from TClass cl.
virtual void	Inspect () const
	Dump contents of this object in a graphics canvas.
void	InvertBit (UInt_t f)
Bool_t	IsDestructed () const
	IsDestructed.
virtual Bool_t	IsEqual (const TObject *obj) const
	Default equal comparison (objects are equal if they have the same address in memory).
virtual Bool_t	IsFolder () const
	Returns kTRUE in case object contains browsable objects (like containers or lists of other objects).
R__ALWAYS_INLINE Bool_t	IsOnHeap () const
R__ALWAYS_INLINE Bool_t	IsZombie () const
void	MayNotUse (const char *method) const
	Use this method to signal that a method (defined in a base class) may not be called in a derived class (in principle against good design since a child class should not provide less functionality than its parent, however, sometimes it is necessary).
virtual Bool_t	Notify ()
	This method must be overridden to handle object notification (the base implementation is no-op).
void	Obsolete (const char *method, const char *asOfVers, const char *removedFromVers) const
	Use this method to declare a method obsolete.
void	operator delete (void *ptr)
	Operator delete.
void	operator delete (void *ptr, void *vp)
	Only called by placement new when throwing an exception.
void	operator delete[] (void *ptr)
	Operator delete [].
void	operator delete[] (void *ptr, void *vp)
	Only called by placement new[] when throwing an exception.
void *	operator new (size_t sz)
void *	operator new (size_t sz, void *vp)
void *	operator new[] (size_t sz)
void *	operator new[] (size_t sz, void *vp)
TObject &	operator= (const TObject &rhs)
	TObject assignment operator.
virtual void	Pop ()
	Pop on object drawn in a pad to the top of the display list.
virtual Int_t	Read (const char *name)
	Read contents of object with specified name from the current directory.
void	ResetBit (UInt_t f)
void	SetBit (UInt_t f)
void	SetBit (UInt_t f, Bool_t set)
	Set or unset the user status bits as specified in f.
virtual void	SetDrawOption (Option_t *option="")
	Set drawing option for object.
virtual void	SetUniqueID (UInt_t uid)
	Set the unique object id.
void	StreamerNVirtual (TBuffer &ClassDef_StreamerNVirtual_b)
virtual void	SysError (const char *method, const char *msgfmt,...) const
	Issue system error message.
R__ALWAYS_INLINE Bool_t	TestBit (UInt_t f) const
Int_t	TestBits (UInt_t f) const
virtual void	Warning (const char *method, const char *msgfmt,...) const
	Issue warning message.
virtual Int_t	Write (const char *name=nullptr, Int_t option=0, Int_t bufsize=0)
	Write this object to the current directory.
virtual Int_t	Write (const char *name=nullptr, Int_t option=0, Int_t bufsize=0) const
	Write this object to the current directory.
Public Member Functions inherited from TAttLine
	TAttLine ()
	AttLine default constructor.
	TAttLine (Color_t lcolor, Style_t lstyle, Width_t lwidth)
	AttLine normal constructor.
virtual	~TAttLine ()
	AttLine destructor.
void	Copy (TAttLine &attline) const
	Copy this line attributes to a new TAttLine.
Int_t	DistancetoLine (Int_t px, Int_t py, Double_t xp1, Double_t yp1, Double_t xp2, Double_t yp2)
	Compute distance from point px,py to a line.
virtual Color_t	GetLineColor () const
	Return the line color.
virtual Style_t	GetLineStyle () const
	Return the line style.
virtual Width_t	GetLineWidth () const
	Return the line width.
virtual void	Modify ()
	Change current line attributes if necessary.
virtual void	ResetAttLine (Option_t *option="")
	Reset this line attributes to default values.
virtual void	SaveLineAttributes (std::ostream &out, const char *name, Int_t coldef=1, Int_t stydef=1, Int_t widdef=1)
	Save line attributes as C++ statement(s) on output stream out.
virtual void	SetLineAttributes ()
	Invoke the DialogCanvas Line attributes.
virtual void	SetLineColor (Color_t lcolor)
	Set the line color.
virtual void	SetLineColorAlpha (Color_t lcolor, Float_t lalpha)
	Set a transparent line color.
virtual void	SetLineStyle (Style_t lstyle)
	Set the line style.
virtual void	SetLineWidth (Width_t lwidth)
	Set the line width.
void	StreamerNVirtual (TBuffer &ClassDef_StreamerNVirtual_b)
Public Member Functions inherited from TAttFill
	TAttFill ()
	AttFill default constructor.
	TAttFill (Color_t fcolor, Style_t fstyle)
	AttFill normal constructor.
virtual	~TAttFill ()
	AttFill destructor.
void	Copy (TAttFill &attfill) const
	Copy this fill attributes to a new TAttFill.
virtual Color_t	GetFillColor () const
	Return the fill area color.
virtual Style_t	GetFillStyle () const
	Return the fill area style.
virtual Bool_t	IsTransparent () const
virtual void	Modify ()
	Change current fill area attributes if necessary.
virtual void	ResetAttFill (Option_t *option="")
	Reset this fill attributes to default values.
virtual void	SaveFillAttributes (std::ostream &out, const char *name, Int_t coldef=1, Int_t stydef=1001)
	Save fill attributes as C++ statement(s) on output stream out.
virtual void	SetFillAttributes ()
	Invoke the DialogCanvas Fill attributes.
virtual void	SetFillColor (Color_t fcolor)
	Set the fill area color.
virtual void	SetFillColorAlpha (Color_t fcolor, Float_t falpha)
	Set a transparent fill color.
virtual void	SetFillStyle (Style_t fstyle)
	Set the fill area style.
void	StreamerNVirtual (TBuffer &ClassDef_StreamerNVirtual_b)
Public Member Functions inherited from TAttMarker
	TAttMarker ()
	TAttMarker default constructor.
	TAttMarker (Color_t color, Style_t style, Size_t msize)
	TAttMarker normal constructor.
virtual	~TAttMarker ()
	TAttMarker destructor.
void	Copy (TAttMarker &attmarker) const
	Copy this marker attributes to a new TAttMarker.
virtual Color_t	GetMarkerColor () const
	Return the marker color.
virtual Size_t	GetMarkerSize () const
	Return the marker size.
virtual Style_t	GetMarkerStyle () const
	Return the marker style.
virtual void	Modify ()
	Change current marker attributes if necessary.
virtual void	ResetAttMarker (Option_t *toption="")
	Reset this marker attributes to the default values.
virtual void	SaveMarkerAttributes (std::ostream &out, const char *name, Int_t coldef=1, Int_t stydef=1, Int_t sizdef=1)
	Save line attributes as C++ statement(s) on output stream out.
virtual void	SetMarkerAttributes ()
	Invoke the DialogCanvas Marker attributes.
virtual void	SetMarkerColor (Color_t mcolor=1)
	Set the marker color.
virtual void	SetMarkerColorAlpha (Color_t mcolor, Float_t malpha)
	Set a transparent marker color.
virtual void	SetMarkerSize (Size_t msize=1)
	Set the marker size.
virtual void	SetMarkerStyle (Style_t mstyle=1)
	Set the marker style.
void	StreamerNVirtual (TBuffer &ClassDef_StreamerNVirtual_b)

Static Public Member Functions
static TClass *	Class ()
static const char *	Class_Name ()
static constexpr Version_t	Class_Version ()
static Bool_t	CompareArg (const TGraph *gr, Int_t left, Int_t right)
	Return kTRUE if point number "left"'s argument (angle with respect to positive x-axis) is bigger than that of point number "right".
static Bool_t	CompareRadius (const TGraph *gr, Int_t left, Int_t right)
	Return kTRUE if point number "left"'s distance to origin is bigger than that of point number "right".
static Bool_t	CompareX (const TGraph *gr, Int_t left, Int_t right)
	Return kTRUE if fX[left] > fX[right]. Can be used by Sort.
static Bool_t	CompareY (const TGraph *gr, Int_t left, Int_t right)
	Return kTRUE if fY[left] > fY[right]. Can be used by Sort.
static const char *	DeclFileName ()
Static Public Member Functions inherited from TNamed
static TClass *	Class ()
static const char *	Class_Name ()
static constexpr Version_t	Class_Version ()
static const char *	DeclFileName ()
Static Public Member Functions inherited from TObject
static TClass *	Class ()
static const char *	Class_Name ()
static constexpr Version_t	Class_Version ()
static const char *	DeclFileName ()
static Longptr_t	GetDtorOnly ()
	Return destructor only flag.
static Bool_t	GetObjectStat ()
	Get status of object stat flag.
static void	SetDtorOnly (void *obj)
	Set destructor only flag.
static void	SetObjectStat (Bool_t stat)
	Turn on/off tracking of objects in the TObjectTable.
Static Public Member Functions inherited from TAttLine
static TClass *	Class ()
static const char *	Class_Name ()
static constexpr Version_t	Class_Version ()
static const char *	DeclFileName ()
Static Public Member Functions inherited from TAttFill
static TClass *	Class ()
static const char *	Class_Name ()
static constexpr Version_t	Class_Version ()
static const char *	DeclFileName ()
Static Public Member Functions inherited from TAttMarker
static TClass *	Class ()
static const char *	Class_Name ()
static constexpr Version_t	Class_Version ()
static const char *	DeclFileName ()
static Width_t	GetMarkerLineWidth (Style_t style)
	Internal helper function that returns the line width of the given marker style (0 = filled marker)
static Style_t	GetMarkerStyleBase (Style_t style)
	Internal helper function that returns the corresponding marker style with line width 1 for the given style.

Protected Member Functions
virtual Double_t **	Allocate (Int_t newsize)
	Allocate internal data structures for newsize points.
Double_t **	AllocateArrays (Int_t Narrays, Int_t arraySize)
	Allocate arrays.
virtual void	CopyAndRelease (Double_t **newarrays, Int_t ibegin, Int_t iend, Int_t obegin)
	Copy points from fX and fY to arrays[0] and arrays[1] or to fX and fY if arrays == 0 and ibegin != iend.
virtual Bool_t	CopyPoints (Double_t **newarrays, Int_t ibegin, Int_t iend, Int_t obegin)
	Copy points from fX and fY to arrays[0] and arrays[1] or to fX and fY if arrays == 0 and ibegin != iend.
Bool_t	CtorAllocate ()
	In constructors set fNpoints than call this method.
virtual Bool_t	DoMerge (const TGraph *g)
	protected function to perform the merge operation of a graph
Double_t **	ExpandAndCopy (Int_t size, Int_t iend)
	if size > fMaxSize allocate new arrays of 2*size points and copy iend first points.
virtual void	FillZero (Int_t begin, Int_t end, Bool_t from_ctor=kTRUE)
	Set zero values for point arrays in the range [begin, end) Should be redefined in descendant classes.
TString	SaveArray (std::ostream &out, const char *suffix, Int_t frameNumber, Double_t *arr)
	Save array as C++ code Returns name of created array.
void	SaveHistogramAndFunctions (std::ostream &out, const char *varname, Int_t &frameNumber, Option_t *option)
	Save histogram and list of functions of TGraph as C++ statement Used in all TGraph-derived classes.
Double_t **	ShrinkAndCopy (Int_t size, Int_t iend)
	if size*2 <= fMaxSize allocate new arrays of size points, copy points [0,oend).
virtual void	SwapPoints (Int_t pos1, Int_t pos2)
	Swap points.
virtual void	UpdateArrays (const std::vector< Int_t > &sorting_indices, Int_t numSortedPoints, Int_t low)
	Update the fX and fY arrays with the sorted values.
Protected Member Functions inherited from TObject
virtual void	DoError (int level, const char *location, const char *fmt, va_list va) const
	Interface to ErrorHandler (protected).
void	MakeZombie ()

Static Protected Member Functions
static void	SwapValues (Double_t *arr, Int_t pos1, Int_t pos2)
	Swap values.

Protected Attributes
TList *	fFunctions
	Pointer to list of functions (fits and user)
TH1F *	fHistogram
	Pointer to histogram used for drawing axis.
Double_t	fMaximum
	Maximum value for plotting along y.
Int_t	fMaxSize
	!Current dimension of arrays fX and fY
Double_t	fMinimum
	Minimum value for plotting along y.
Int_t	fNpoints
	Number of points <= fMaxSize.
Double_t *	fX
	[fNpoints] array of X points
Double_t *	fY
	[fNpoints] array of Y points
Protected Attributes inherited from TNamed
TString	fName
TString	fTitle
Protected Attributes inherited from TAttLine
Color_t	fLineColor
	Line color.
Style_t	fLineStyle
	Line style.
Width_t	fLineWidth
	Line width.
Protected Attributes inherited from TAttFill
Color_t	fFillColor
	Fill area color.
Style_t	fFillStyle
	Fill area style.
Protected Attributes inherited from TAttMarker
Color_t	fMarkerColor
	Marker color.
Size_t	fMarkerSize
	Marker size.
Style_t	fMarkerStyle
	Marker style.

Additional Inherited Members
Protected Types inherited from TObject
enum	{ kOnlyPrepStep = (1ULL << ( 3 )) }

#include <TGraph.h>

Inheritance diagram for TGraph:

Member Enumeration Documentation

EStatusBits

enum TGraph::EStatusBits

Enumerator
kNoStats	Don't draw stats box.
kClipFrame	Clip to the frame boundary.
kResetHisto	fHistogram must be reset in GetHistogram
kNotEditable	Bit set if graph is non editable.
kIsSortedX	Graph is sorted in X points.
kIsHighlight	Bit set if graph is highlight.

Definition at line 73 of file TGraph.h.

Constructor & Destructor Documentation

TGraph() [1/12]

TGraph::TGraph

(

)

Graph default constructor.

Definition at line 108 of file TGraph.cxx.

TGraph() [2/12]

TGraph::TGraph

(

Int_t

n

)

Constructor with only the number of points set the arrays x and y will be set later.

Definition at line 118 of file TGraph.cxx.

TGraph() [3/12]

TGraph::TGraph	(	Int_t	n,
		const Int_t *	x,
		const Int_t *	y
	)

Graph normal constructor with ints.

Definition at line 129 of file TGraph.cxx.

TGraph() [4/12]

TGraph::TGraph	(	Int_t	n,
		const Float_t *	x,
		const Float_t *	y
	)

Graph normal constructor with floats.

Definition at line 147 of file TGraph.cxx.

TGraph() [5/12]

TGraph::TGraph	(	Int_t	n,
		const Double_t *	x,
		const Double_t *	y
	)

Graph normal constructor with doubles.

Definition at line 184 of file TGraph.cxx.

TGraph() [6/12]

TGraph::TGraph	(	Int_t	n,
		const Double_t *	y,
		Double_t	start = 0.,
		Double_t	step = 1.
	)

Default X-Points constructor.

The points along the x-axis get the default values start, start+step, start+2*step, start+3*step, etc ...

Definition at line 166 of file TGraph.cxx.

TGraph() [7/12]

TGraph::TGraph

(

const TGraph &

gr

)

Copy constructor for this graph.

Definition at line 201 of file TGraph.cxx.

TGraph() [8/12]

TGraph::TGraph	(	const TVectorF &	vx,
		const TVectorF &	vy
	)

Graph constructor with two vectors of floats in input A graph is build with the X coordinates taken from vx and Y coord from vy The number of points in the graph is the minimum of number of points in vx and vy.

Definition at line 297 of file TGraph.cxx.

TGraph() [9/12]

TGraph::TGraph	(	const TVectorD &	vx,
		const TVectorD &	vy
	)

Graph constructor with two vectors of doubles in input A graph is build with the X coordinates taken from vx and Y coord from vy The number of points in the graph is the minimum of number of points in vx and vy.

Definition at line 316 of file TGraph.cxx.

TGraph() [10/12]

TGraph::TGraph

(

const TH1 *

h

)

Graph constructor importing its parameters from the TH1 object passed as argument.

Definition at line 332 of file TGraph.cxx.

TGraph() [11/12]

TGraph::TGraph	(	const TF1 *	f,
		Option_t *	option = ""
	)

Graph constructor importing its parameters from the TF1 object passed as argument.

• if option =="" (default), a TGraph is created with points computed at the fNpx points of f.
• if option =="d", a TGraph is created with points computed with the derivatives at the fNpx points of f.
• if option =="i", a TGraph is created with points computed with the integral at the fNpx points of f.
• if option =="I", a TGraph is created with points computed with the integral at the fNpx+1 points of f and the integral is normalized to 1.

Definition at line 374 of file TGraph.cxx.

TGraph() [12/12]

TGraph::TGraph	(	const char *	filename,
		const char *	format = "%lg %lg",
		Option_t *	option = ""
	)

Graph constructor reading input from filename.

filename is assumed to contain at least two columns of numbers. The string format is by default "%lg %lg". This is a standard c formatting for scanf().

If columns of numbers should be skipped, a "%*lg" or "%*s" for each column can be added, e.g. "%lg %*lg %lg" would read x-values from the first and y-values from the third column.

For files separated by a specific delimiter different from ' ' and '\t' (e.g. ';' in csv files) you can avoid using %*s to bypass this delimiter by explicitly specify the option argument, e.g. option=" \\t,;" for columns of figures separated by any of these characters (' ', '\t', ',', ';') used once (e.g. "1;1") or in a combined way (" 1;,;; 1"). Note in that case, the instantiation is about two times slower.

Definition at line 438 of file TGraph.cxx.

~TGraph()

TGraph::~TGraph ( )

override

Graph default destructor.

Definition at line 561 of file TGraph.cxx.

Member Function Documentation

AddPoint()

virtual void TGraph::AddPoint ( Double_t  x, Double_t  y  )

inlinevirtual

Append a new point to the graph.

Definition at line 97 of file TGraph.h.

Allocate()

Double_t ** TGraph::Allocate ( Int_t  newsize )

protectedvirtual

Allocate internal data structures for newsize points.

Reimplemented in TGraphAsymmErrors, TGraphBentErrors, TGraphErrors, and TGraphMultiErrors.

Definition at line 585 of file TGraph.cxx.

AllocateArrays()

Double_t ** TGraph::AllocateArrays ( Int_t  Narrays, Int_t  arraySize  )

protected

Allocate arrays.

Definition at line 593 of file TGraph.cxx.

Apply()

void TGraph::Apply ( TF1 *  f )

virtual

Apply function f to all the data points f may be a 1-D function TF1 or 2-d function TF2 The Y values of the graph are replaced by the new values computed using the function.

Reimplemented in TGraphAsymmErrors, TGraphBentErrors, TGraphErrors, and TGraphMultiErrors.

Definition at line 616 of file TGraph.cxx.

Browse()

void TGraph::Browse ( TBrowser *  b )

overridevirtual

Browse.

Reimplemented from TObject.

Definition at line 629 of file TGraph.cxx.

Chisquare()

Double_t TGraph::Chisquare ( TF1 *  func, Option_t *  option = ""  ) const

virtual

Return the chisquare of this graph with respect to f1.

The chisquare is computed as the sum of the quantity below at each point:

\[ \frac{(y-f1(x))^{2}}{ey^{2}+(\frac{1}{2}(exl+exh)f1'(x))^{2}} \]

where x and y are the graph point coordinates and f1'(x) is the derivative of function f1(x). This method to approximate the uncertainty in y because of the errors in x, is called "effective variance" method. In case of a pure TGraph, the denominator is 1. In case of a TGraphErrors or TGraphAsymmErrors the errors are taken into account. By default the range of the graph is used whatever function range. Use option "R" to use the function range

Definition at line 655 of file TGraph.cxx.

Class()

static TClass * TGraph::Class ( )

static

Returns

TClass describing this class

Class_Name()

static const char * TGraph::Class_Name ( )

static

Returns

Name of this class

Class_Version()

static constexpr Version_t TGraph::Class_Version ( )

inlinestaticconstexpr

Returns

Version of this class

Definition at line 200 of file TGraph.h.

CompareArg()

Bool_t TGraph::CompareArg ( const TGraph *  gr, Int_t  left, Int_t  right  )

static

Return kTRUE if point number "left"'s argument (angle with respect to positive x-axis) is bigger than that of point number "right".

Can be used by Sort.

Definition at line 672 of file TGraph.cxx.

CompareRadius()

Bool_t TGraph::CompareRadius ( const TGraph *  gr, Int_t  left, Int_t  right  )

static

Return kTRUE if point number "left"'s distance to origin is bigger than that of point number "right".

Can be used by Sort.

Definition at line 700 of file TGraph.cxx.

CompareX()

Bool_t TGraph::CompareX ( const TGraph *  gr, Int_t  left, Int_t  right  )

static

Return kTRUE if fX[left] > fX[right]. Can be used by Sort.

Definition at line 683 of file TGraph.cxx.

CompareY()

Bool_t TGraph::CompareY ( const TGraph *  gr, Int_t  left, Int_t  right  )

static

Return kTRUE if fY[left] > fY[right]. Can be used by Sort.

Definition at line 691 of file TGraph.cxx.

ComputeRange()

void TGraph::ComputeRange ( Double_t &  xmin, Double_t &  ymin, Double_t &  xmax, Double_t &  ymax  ) const

virtual

Compute the x/y range of the points in this graph.

Reimplemented in TGraphAsymmErrors, TGraphBentErrors, TGraphErrors, and TGraphMultiErrors.

Definition at line 709 of file TGraph.cxx.

CopyAndRelease()

void TGraph::CopyAndRelease ( Double_t **  newarrays, Int_t  ibegin, Int_t  iend, Int_t  obegin  )

protectedvirtual

Copy points from fX and fY to arrays[0] and arrays[1] or to fX and fY if arrays == 0 and ibegin != iend.

If newarrays is non null, replace fX, fY with pointers from newarrays[0,1]. Delete newarrays, old fX and fY

Reimplemented in TGraphAsymmErrors, TGraphBentErrors, TGraphErrors, and TGraphMultiErrors.

Definition at line 740 of file TGraph.cxx.

CopyPoints()

Bool_t TGraph::CopyPoints ( Double_t **  newarrays, Int_t  ibegin, Int_t  iend, Int_t  obegin  )

protectedvirtual

Copy points from fX and fY to arrays[0] and arrays[1] or to fX and fY if arrays == 0 and ibegin != iend.

Reimplemented in TGraphAsymmErrors, TGraphBentErrors, TGraphErrors, and TGraphMultiErrors.

Definition at line 757 of file TGraph.cxx.

CtorAllocate()

Bool_t TGraph::CtorAllocate ( )

protected

In constructors set fNpoints than call this method.

Return kFALSE if the graph will contain no points. Note: This function should be called only from the constructor since it does not delete previously existing arrays

Definition at line 783 of file TGraph.cxx.

DeclFileName()

static const char * TGraph::DeclFileName ( )

inlinestatic

Returns

Name of the file containing the class declaration

Definition at line 200 of file TGraph.h.

DistancetoPrimitive()

Int_t TGraph::DistancetoPrimitive ( Int_t  px, Int_t  py  )

overridevirtual

Compute distance from point px,py to a graph.

Compute the closest distance of approach from point px,py to this line. The distance is computed in pixels units.

Reimplemented from TObject.

Definition at line 853 of file TGraph.cxx.

DoMerge()

Bool_t TGraph::DoMerge ( const TGraph *  g )

protectedvirtual

protected function to perform the merge operation of a graph

Reimplemented in TGraphAsymmErrors, TGraphBentErrors, TGraphErrors, and TGraphMultiErrors.

Definition at line 2649 of file TGraph.cxx.

Draw()

void TGraph::Draw ( Option_t *  option = "" )

overridevirtual

Draw this graph with its current attributes.

The options to draw a graph are described in TGraphPainter class.

Reimplemented from TObject.

Reimplemented in TGraphPolar.

Definition at line 809 of file TGraph.cxx.

DrawGraph() [1/3]

void TGraph::DrawGraph ( Int_t  n, const Double_t *  x = nullptr, const Double_t *  y = nullptr, Option_t *  option = ""  )

virtual

Draw this graph with new attributes.

Definition at line 889 of file TGraph.cxx.

DrawGraph() [2/3]

void TGraph::DrawGraph ( Int_t  n, const Float_t *  x, const Float_t *  y, Option_t *  option = ""  )

virtual

Draw this graph with new attributes.

Definition at line 876 of file TGraph.cxx.

DrawGraph() [3/3]

void TGraph::DrawGraph ( Int_t  n, const Int_t *  x, const Int_t *  y, Option_t *  option = ""  )

virtual

Draw this graph with new attributes.

Definition at line 863 of file TGraph.cxx.

DrawPanel()

void TGraph::DrawPanel ( )

virtual

Display a panel with all graph drawing options.

Definition at line 906 of file TGraph.cxx.

Eval()

Double_t TGraph::Eval ( Double_t  x, TSpline *  spline = nullptr, Option_t *  option = ""  ) const

virtual

Interpolate points in this graph at x using a TSpline.

• if spline==0 and option="" a linear interpolation between the two points close to x is computed. If x is outside the graph range, a linear extrapolation is computed.
• if spline==0 and option="S" a TSpline3 object is created using this graph and the interpolated value from the spline is returned. the internally created spline is deleted on return.

• if spline is specified, it is used to return the interpolated value.

  If the points are sorted in X a binary search is used (significantly faster) One needs to set the bit TGraph::SetBit(TGraph::kIsSortedX) before calling TGraph::Eval to indicate that the graph is sorted in X.

Definition at line 927 of file TGraph.cxx.

ExecuteEvent()

void TGraph::ExecuteEvent ( Int_t  event, Int_t  px, Int_t  py  )

overridevirtual

Execute action corresponding to one event.

This member function is called when a graph is clicked with the locator

If Left button clicked on one of the line end points, this point follows the cursor until button is released.

if Middle button clicked, the line is moved parallel to itself until the button is released.

Reimplemented from TObject.

Definition at line 1030 of file TGraph.cxx.

Expand() [1/2]

void TGraph::Expand ( Int_t  newsize )

virtual

If array sizes <= newsize, expand storage to 2*newsize.

Definition at line 1039 of file TGraph.cxx.

Expand() [2/2]

void TGraph::Expand ( Int_t  newsize, Int_t  step  )

virtual

If graph capacity is less than newsize points then make array sizes equal to least multiple of step to contain newsize points.

Definition at line 1049 of file TGraph.cxx.

ExpandAndCopy()

Double_t ** TGraph::ExpandAndCopy ( Int_t  size, Int_t  iend  )

protected

if size > fMaxSize allocate new arrays of 2*size points and copy iend first points.

Return pointer to new arrays.

Definition at line 1063 of file TGraph.cxx.

FillZero()

void TGraph::FillZero ( Int_t  begin, Int_t  end, Bool_t  from_ctor = kTRUE  )

protectedvirtual

Set zero values for point arrays in the range [begin, end) Should be redefined in descendant classes.

Reimplemented in TGraphAsymmErrors, TGraphBentErrors, TGraphErrors, and TGraphMultiErrors.

Definition at line 1076 of file TGraph.cxx.

FindObject() [1/2]

TObject * TGraph::FindObject ( const char *  name ) const

overridevirtual

Search object named name in the list of functions.

Reimplemented from TObject.

Definition at line 1085 of file TGraph.cxx.

FindObject() [2/2]

TObject * TGraph::FindObject ( const TObject *  obj ) const

overridevirtual

Search object obj in the list of functions.

Reimplemented from TObject.

Definition at line 1093 of file TGraph.cxx.

Fit() [1/2]

TFitResultPtr TGraph::Fit ( const char *  fname, Option_t *  option = "", Option_t *  goption = "", Axis_t  xmin = 0, Axis_t  xmax = 0  )

virtual

Fit this graph with function with name fname.

This is a different interface to TGraph fitting using TGraph::Fit(TF1 *f1,Option_t *, Option_t *, Axis_t, Axis_t) See there for the details about fitting a TGraph.

The parameter fname is the name of an already predefined function created by TF1 or TF2 Predefined functions such as gaus, expo and poln are automatically created by ROOT.

The parameter fname can also be a formula, accepted by the linear fitter (linear parts divided by "++" sign), for example "x++sin(x)" for fitting "[0]*x+[1]*sin(x)"

Definition at line 1228 of file TGraph.cxx.

Fit() [2/2]

TFitResultPtr TGraph::Fit ( TF1 *  f1, Option_t *  option = "", Option_t *  goption = "", Axis_t  rxmin = 0, Axis_t  rxmax = 0  )

virtual

Fit this graph with function f1.

Parameters

[in]	f1	pointer to the function object
[in]	option	string defining the fit options (see table below).
[in]	goption	specify a list of graphics options. See TGraph::Draw and TGraphPainter for a complete list of these possible options.
[in]	rxmin	lower fitting range
[in]	rxmax	upper fitting range

Graph Fitting Options

The list of fit options is given in parameter option.

option	description
"S"	The full result of the fit is returned in the TFitResultPtr. This is needed to get the covariance matrix of the fit. See TFitResult and the base class ROOT::Math::FitResult.
"W"	Ignore all point errors when fitting a TGraphErrors or TGraphAsymmErrors
"F"	Uses the default minimizer (e.g. Minuit) when fitting a linear function (e.g. polN) instead of the linear fitter.
"U"	Uses a user specified objective function (e.g. user providedlikelihood function) defined using TVirtualFitter::SetFCN
"E"	Performs a better parameter errors estimation using the Minos technique for all fit parameters.
"M"	Uses the IMPROVE algorithm (available only in TMinuit). This algorithm attempts improve the found local minimum by searching for a better one.
"Q"	Quiet mode (minimum printing)
"V"	Verbose mode (default is between Q and V)
"+"	Adds this new fitted function to the list of fitted functions. By default, the previous function is deleted and only the last one is kept.
"N"	Does not store the graphics function, does not draw the histogram with the function after fitting.
"0"	Does not draw the histogram and the fitted function after fitting, but in contrast to option "N", it stores the fitted function in the histogram list of functions.
"R"	Fit using a fitting range specified in the function range with TF1::SetRange.
"B"	Use this option when you want to fix one or more parameters and the fitting function is a predefined one (e.g gaus, expo,..), otherwise in case of pre-defined functions, some default initial values and limits are set.
"C"	In case of linear fitting, do no calculate the chisquare (saves CPU time).
"G"	Uses the gradient implemented in TF1::GradientPar for the minimization. This allows to use Automatic Differentiation when it is supported by the provided TF1 function.
"EX0"	When fitting a TGraphErrors or TGraphAsymErrors do not consider errors in the X coordinates
"ROB"	In case of linear fitting, compute the LTS regression coefficients (robust (resistant) regression), using the default fraction of good points "ROB=0.x" - compute the LTS regression coefficients, using 0.x as a fraction of good points

This function is used for fitting also the derived TGraph classes such as TGraphErrors or TGraphAsymmErrors. See the note below on how the errors are used when fitting a TGraphErrors or TGraphAsymmErrors.

The fitting of the TGraph, i.e simple data points without any error associated, is performed using the un-weighted least-square (chi-square) method.

TGraphErrors fit:

In case of a TGraphErrors or TGraphAsymmErrors object, when x errors are present, the error along x, is projected along the y-direction by calculating the function at the points x-ex_low and x+ex_high, where ex_low and ex_high are the corresponding lower and upper error in x. The chi-square is then computed as the sum of the quantity below at each data point:

\[ \frac{(y-f(x))^{2}}{ey^{2}+(\frac{1}{2}(exl+exh)f'(x))^{2}} \]

where x and y are the point coordinates, and ‘f’(x)is the derivative of the functionf(x)`.

In case of asymmetric errors, if the function lies below (above) the data point, ey is ey_low (ey_high).

The approach used to approximate the uncertainty in y because of the errors in x is to make it equal the error in x times the slope of the line. This approach is called "effective variance method" and the implementation is provided in the function FitUtil::EvaluateChi2Effective

Linear fitting:

When the fitting function is linear (contains the ++ sign) or the fitting function is a polynomial, a linear fitter is initialised. To create a linear function, use the following syntax: linear parts separated by ++ sign. Example: to fit the parameters of the function p0*x + p1*sin(x), you can create a TF1 object as

TF1 *f1 = new TF1("f1", "x++sin(x)", xmin, xmax);

For such a TF1 you don't have to set the initial conditions and the linear fitter is used. Going via the linear fitter for functions, linear in parameters, gives a considerable advantage in speed. When using the linear fitting it is also possible to perform a robust fitting with the Least Trimmed Square (LTS) regression algorithm, by using the fit option ROB. See the tutorial fitLinearRobust.C.

Notes on TGraph/TGraphErrors Fitting:

1. By using the "effective variance" method a simple linear regression becomes a non-linear case, which takes several iterations instead of 0 as in the linear case.
2. The effective variance technique assumes that there is no correlation between the x and y coordinate.
3. The standard chi2 (least square) method without error in the coordinates (x) can be forced by using option "EX0"
4. The linear fitter doesn't take into account the errors in x. When fitting a TGraphErrors with a linear functions the errors in x will not be considered. If errors in x are important, use option "F" for linear function fitting.
5. When fitting a TGraph (i.e. no errors associated with each point), a correction is applied to the errors on the parameters with the following formula: parameter_error *= sqrt(chisquare/(ndf-1))

General Fitting documentation

See in TH1::Fit for the documentation of

• Fit Result
• Fit Status
• Fit Statistics Box
• Fitting in a Range
• Setting Initial Conditions

Definition at line 1205 of file TGraph.cxx.

FitPanel()

void TGraph::FitPanel ( )

virtual

Display a GUI panel with all graph fit options.

See class TFitEditor for example

Definition at line 1248 of file TGraph.cxx.

GetCorrelationFactor()

Double_t TGraph::GetCorrelationFactor ( ) const

virtual

Return graph correlation factor.

Definition at line 1270 of file TGraph.cxx.

GetCovariance()

Double_t TGraph::GetCovariance ( ) const

virtual

Return covariance of vectors x,y.

Definition at line 1282 of file TGraph.cxx.

GetEditable()

Bool_t TGraph::GetEditable

(

)

const

Return kTRUE if kNotEditable bit is not set, kFALSE otherwise.

Definition at line 2265 of file TGraph.cxx.

GetErrorX()

Double_t TGraph::GetErrorX ( Int_t  bin ) const

virtual

It always returns a negative value. Real implementation in TGraphErrors.

Reimplemented in TGraphAsymmErrors, TGraphBentErrors, TGraphErrors, and TGraphMultiErrors.

Definition at line 1335 of file TGraph.cxx.

GetErrorXhigh()

Double_t TGraph::GetErrorXhigh ( Int_t  bin ) const

virtual

It always returns a negative value.

Real implementation in TGraphErrors and TGraphAsymmErrors

Reimplemented in TGraphBentErrors, TGraphErrors, TGraphAsymmErrors, and TGraphMultiErrors.

Definition at line 1352 of file TGraph.cxx.

GetErrorXlow()

Double_t TGraph::GetErrorXlow ( Int_t  bin ) const

virtual

It always returns a negative value.

Real implementation in TGraphErrors and TGraphAsymmErrors

Reimplemented in TGraphBentErrors, TGraphErrors, TGraphAsymmErrors, and TGraphMultiErrors.

Definition at line 1361 of file TGraph.cxx.

GetErrorY()

Double_t TGraph::GetErrorY ( Int_t  bin ) const

virtual

It always returns a negative value. Real implementation in TGraphErrors.

Reimplemented in TGraphAsymmErrors, TGraphBentErrors, TGraphErrors, and TGraphMultiErrors.

Definition at line 1343 of file TGraph.cxx.

GetErrorYhigh()

Double_t TGraph::GetErrorYhigh ( Int_t  bin ) const

virtual

It always returns a negative value.

Real implementation in TGraphErrors and TGraphAsymmErrors

Reimplemented in TGraphBentErrors, TGraphErrors, TGraphAsymmErrors, and TGraphMultiErrors.

Definition at line 1370 of file TGraph.cxx.

GetErrorYlow()

Double_t TGraph::GetErrorYlow ( Int_t  bin ) const

virtual

It always returns a negative value.

Real implementation in TGraphErrors and TGraphAsymmErrors

Reimplemented in TGraphBentErrors, TGraphErrors, TGraphAsymmErrors, and TGraphMultiErrors.

Definition at line 1379 of file TGraph.cxx.

GetEX()

virtual Double_t * TGraph::GetEX ( ) const

inlinevirtual

Reimplemented in TGraphErrors.

Definition at line 139 of file TGraph.h.

GetEXhigh()

virtual Double_t * TGraph::GetEXhigh ( ) const

inlinevirtual

Reimplemented in TGraphAsymmErrors, TGraphBentErrors, and TGraphMultiErrors.

Definition at line 141 of file TGraph.h.

GetEXhighd()

virtual Double_t * TGraph::GetEXhighd ( ) const

inlinevirtual

Reimplemented in TGraphBentErrors.

Definition at line 146 of file TGraph.h.

GetEXlow()

virtual Double_t * TGraph::GetEXlow ( ) const

inlinevirtual

Reimplemented in TGraphAsymmErrors, TGraphBentErrors, and TGraphMultiErrors.

Definition at line 142 of file TGraph.h.

GetEXlowd()

virtual Double_t * TGraph::GetEXlowd ( ) const

inlinevirtual

Reimplemented in TGraphBentErrors.

Definition at line 145 of file TGraph.h.

GetEY()

virtual Double_t * TGraph::GetEY ( ) const

inlinevirtual

Reimplemented in TGraphErrors.

Definition at line 140 of file TGraph.h.

GetEYhigh()

virtual Double_t * TGraph::GetEYhigh ( ) const

inlinevirtual

Reimplemented in TGraphAsymmErrors, TGraphBentErrors, and TGraphMultiErrors.

Definition at line 143 of file TGraph.h.

GetEYhighd()

virtual Double_t * TGraph::GetEYhighd ( ) const

inlinevirtual

Reimplemented in TGraphBentErrors.

Definition at line 148 of file TGraph.h.

GetEYlow()

virtual Double_t * TGraph::GetEYlow ( ) const

inlinevirtual

Reimplemented in TGraphAsymmErrors, TGraphBentErrors, and TGraphMultiErrors.

Definition at line 144 of file TGraph.h.

GetEYlowd()

virtual Double_t * TGraph::GetEYlowd ( ) const

inlinevirtual

Reimplemented in TGraphBentErrors.

Definition at line 147 of file TGraph.h.

GetFunction()

TF1 * TGraph::GetFunction

(

const char *

name

)

const

Return pointer to function with name.

Functions such as TGraph::Fit store the fitted function in the list of functions of this graph.

Definition at line 1390 of file TGraph.cxx.

GetHistogram()

TH1F * TGraph::GetHistogram ( ) const

virtual

Returns a pointer to the histogram used to draw the axis Takes into account the two following cases.

1. option 'A' was specified in TGraph::Draw. Return fHistogram
2. user had called TPad::DrawFrame. return pointer to hframe histogram

Definition at line 1402 of file TGraph.cxx.

GetListOfFunctions()

TList * TGraph::GetListOfFunctions ( ) const

inline

Definition at line 124 of file TGraph.h.

GetMaximum()

Double_t TGraph::GetMaximum ( ) const

inline

Definition at line 149 of file TGraph.h.

GetMaxSize()

Int_t TGraph::GetMaxSize ( ) const

inline

Definition at line 129 of file TGraph.h.

GetMean()

Double_t TGraph::GetMean ( Int_t  axis = 1 ) const

virtual

Return mean value of X (axis=1) or Y (axis=2)

Definition at line 1298 of file TGraph.cxx.

GetMinimum()

Double_t TGraph::GetMinimum ( ) const

inline

Definition at line 150 of file TGraph.h.

GetN()

Int_t TGraph::GetN ( ) const

inline

Definition at line 130 of file TGraph.h.

GetObjectInfo()

char * TGraph::GetObjectInfo ( Int_t  px, Int_t  py  ) const

overridevirtual

Implementation to get information on point of graph at cursor position Adapted from class TH1.

Reimplemented from TObject.

Definition at line 1559 of file TGraph.cxx.

GetPoint()

Int_t TGraph::GetPoint ( Int_t  i, Double_t &  x, Double_t &  y  ) const

virtual

Get x and y values for point number i.

The function returns -1 in case of an invalid request or the point number otherwise

Definition at line 1507 of file TGraph.cxx.

GetPointX()

Double_t TGraph::GetPointX ( Int_t  i ) const

virtual

Get x value for point i.

Definition at line 1518 of file TGraph.cxx.

GetPointY()

Double_t TGraph::GetPointY ( Int_t  i ) const

virtual

Get y value for point i.

Definition at line 1529 of file TGraph.cxx.

GetRMS()

Double_t TGraph::GetRMS ( Int_t  axis = 1 ) const

virtual

Return RMS of X (axis=1) or Y (axis=2)

Definition at line 1313 of file TGraph.cxx.

GetX()

Double_t * TGraph::GetX ( ) const

inline

Definition at line 137 of file TGraph.h.

GetXaxis()

TAxis * TGraph::GetXaxis

(

)

const

Get x axis of the graph.

Definition at line 1540 of file TGraph.cxx.

GetY()

Double_t * TGraph::GetY ( ) const

inline

Definition at line 138 of file TGraph.h.

GetYaxis()

TAxis * TGraph::GetYaxis

(

)

const

Get y axis of the graph.

Definition at line 1549 of file TGraph.cxx.

InitExpo()

void TGraph::InitExpo ( Double_t  xmin = 0, Double_t  xmax = 0  )

virtual

Compute Initial values of parameters for an exponential.

Definition at line 1632 of file TGraph.cxx.

InitGaus()

void TGraph::InitGaus ( Double_t  xmin = 0, Double_t  xmax = 0  )

virtual

Compute Initial values of parameters for a gaussian.

Definition at line 1594 of file TGraph.cxx.

InitPolynom()

void TGraph::InitPolynom ( Double_t  xmin = 0, Double_t  xmax = 0  )

virtual

Compute Initial values of parameters for a polynom.

Definition at line 1653 of file TGraph.cxx.

InsertPoint()

Int_t TGraph::InsertPoint ( )

virtual

Insert a new point at the mouse position.

Definition at line 1673 of file TGraph.cxx.

InsertPointBefore()

void TGraph::InsertPointBefore ( Int_t  ipoint, Double_t  x, Double_t  y  )

virtual

Insert a new point with coordinates (x,y) before the point number ipoint.

Definition at line 1723 of file TGraph.cxx.

Integral()

Double_t TGraph::Integral ( Int_t  first = 0, Int_t  last = -1  ) const

virtual

Integrate the TGraph data within a given (index) range.

Note that this function computes the area of the polygon enclosed by the points of the TGraph. The polygon segments, which are defined by the points of the TGraph, do not need to form a closed polygon, since the last polygon segment, which closes the polygon, is taken as the line connecting the last TGraph point with the first one. It is clear that the order of the point is essential in defining the polygon. Also note that the segments should not intersect.

NB:

• if last=-1 (default) last is set to the last point.
• if (first <0) the first point (0) is taken.

Method:

There are many ways to calculate the surface of a polygon. It all depends on what kind of data you have to deal with. The most evident solution would be to divide the polygon in triangles and calculate the surface of them. But this can quickly become complicated as you will have to test every segments of every triangles and check if they are intersecting with a current polygon's segment or if it goes outside the polygon. Many calculations that would lead to many problems...

The solution (implemented by R.Brun)

Fortunately for us, there is a simple way to solve this problem, as long as the polygon's segments don't intersect. It takes the x coordinate of the current vertex and multiply it by the y coordinate of the next vertex. Then it subtracts from it the result of the y coordinate of the current vertex multiplied by the x coordinate of the next vertex. Then divide the result by 2 to get the surface/area.

Sources

• http://forums.wolfram.com/mathgroup/archive/1998/Mar/msg00462.html
• http://stackoverflow.com/questions/451426/how-do-i-calculate-the-surface-area-of-a-2d-polygon

Definition at line 1782 of file TGraph.cxx.

IsA()

TClass * TGraph::IsA ( ) const

inlineoverridevirtual

Returns

TClass describing current object

Reimplemented from TObject.

Reimplemented in TGraphPolar, TGraphQQ, TGraphAsymmErrors, TGraphBentErrors, TGraphErrors, and TGraphMultiErrors.

Definition at line 200 of file TGraph.h.

IsEditable()

virtual Bool_t TGraph::IsEditable ( ) const

inlinevirtual

Definition at line 164 of file TGraph.h.

IsHighlight()

virtual Bool_t TGraph::IsHighlight ( ) const

inlinevirtual

Definition at line 165 of file TGraph.h.

IsInside()

Int_t TGraph::IsInside ( Double_t  x, Double_t  y  ) const

virtual

Return 1 if the point (x,y) is inside the polygon defined by the graph vertices 0 otherwise.

Algorithm:

The loop is executed with the end-point coordinates of a line segment (X1,Y1)-(X2,Y2) and the Y-coordinate of a horizontal line. The counter inter is incremented if the line (X1,Y1)-(X2,Y2) intersects the horizontal line. In this case XINT is set to the X-coordinate of the intersection point. If inter is an odd number, then the point x,y is within the polygon.

Definition at line 1815 of file TGraph.cxx.

LeastSquareFit()

void TGraph::LeastSquareFit ( Int_t  m, Double_t *  a, Double_t  xmin = 0, Double_t  xmax = 0  )

virtual

Least squares polynomial fitting without weights.

Parameters

[in]	m	number of parameters
[in]	a	array of parameters
[in]	xmin	1st point number to fit (default =0)
[in]	xmax	last point number to fit (default=fNpoints-1)

based on CERNLIB routine LSQ: Translated to C++ by Rene Brun

Definition at line 1830 of file TGraph.cxx.

LeastSquareLinearFit()

void TGraph::LeastSquareLinearFit ( Int_t  ndata, Double_t &  a0, Double_t &  a1, Int_t &  ifail, Double_t  xmin = 0, Double_t  xmax = 0  )

virtual

Least square linear fit without weights.

Fit a straight line (a0 + a1*x) to the data in this graph.

Parameters

[in]	ndata	if ndata<0, fits the logarithm of the graph (used in InitExpo() to set the initial parameter values for a fit with exponential function.
[in]	a0	constant
[in]	a1	slope
[in]	ifail	return parameter indicating the status of the fit (ifail=0, fit is OK)
[in]	xmin,xmax	fitting range

extracted from CERNLIB LLSQ: Translated to C++ by Rene Brun

Definition at line 1905 of file TGraph.cxx.

Merge()

Int_t TGraph::Merge ( TCollection *  li )

virtual

Adds all graphs from the collection to this graph.

Returns the total number of points in the result or -1 in case of an error.

Reimplemented in TGraphAsymmErrors, and TGraphErrors.

Definition at line 2631 of file TGraph.cxx.

MovePoints()

void TGraph::MovePoints ( Double_t  dx, Double_t  dy, Bool_t  logx = kFALSE, Bool_t  logy = kFALSE  )

virtual

Move all graph points on specified values dx,dy If log argument specified, calculation done in logarithmic scale like: new_value = exp( log(old_value) + delta );.

Definition at line 2664 of file TGraph.cxx.

operator=()

TGraph & TGraph::operator=

(

const TGraph &

gr

)

Equal operator for this graph.

Definition at line 232 of file TGraph.cxx.

Paint()

void TGraph::Paint ( Option_t *  chopt = "" )

overridevirtual

Draw this graph with its current attributes.

Reimplemented from TObject.

Definition at line 1951 of file TGraph.cxx.

PaintGraph()

void TGraph::PaintGraph	(	Int_t	npoints,
		const Double_t *	x,
		const Double_t *	y,
		Option_t *	chopt
	)

Draw the (x,y) as a graph.

Definition at line 1960 of file TGraph.cxx.

PaintGrapHist()

void TGraph::PaintGrapHist	(	Int_t	npoints,
		const Double_t *	x,
		const Double_t *	y,
		Option_t *	chopt
	)

Draw the (x,y) as a histogram.

Definition at line 1969 of file TGraph.cxx.

PaintStats()

void TGraph::PaintStats ( TF1 *  fit )

virtual

Draw the stats.

Definition at line 1978 of file TGraph.cxx.

Print()

void TGraph::Print ( Option_t *  chopt = "" ) const

overridevirtual

Print graph values.

Reimplemented from TObject.

Reimplemented in TGraphAsymmErrors, TGraphBentErrors, TGraphErrors, and TGraphMultiErrors.

Definition at line 1987 of file TGraph.cxx.

RecursiveRemove()

void TGraph::RecursiveRemove ( TObject *  obj )

overridevirtual

Recursively remove object from the list of functions.

Reimplemented from TObject.

Definition at line 1997 of file TGraph.cxx.

RemovePoint() [1/2]

Int_t TGraph::RemovePoint ( )

virtual

Delete point close to the mouse position Returns index of removed point (or -1 if nothing was changed)

Definition at line 2011 of file TGraph.cxx.

RemovePoint() [2/2]

Int_t TGraph::RemovePoint ( Int_t  ipoint )

virtual

Delete point number ipoint Returns index of removed point (or -1 if nothing was changed)

Definition at line 2039 of file TGraph.cxx.

SaveArray()

TString TGraph::SaveArray ( std::ostream &  out, const char *  suffix, Int_t  frameNumber, Double_t *  arr  )

protected

Save array as C++ code Returns name of created array.

Definition at line 2149 of file TGraph.cxx.

SaveAs()

void TGraph::SaveAs ( const char *  filename, Option_t *  option = ""  ) const

overridevirtual

Save the graph as .csv, .tsv or .txt.

In case of any other extension, fall back to TObject::SaveAs

The result can be immediately imported into Excel, gnuplot, Python or whatever, without the needing to install pyroot, etc.

Parameters

filename	the name of the file where to store the graph
option	some tuning options

The file extension defines the delimiter used:

• .csv : comma
• .tsv : tab
• .txt : space

If option = "title" a title line is generated with the axis titles.

Reimplemented from TObject.

Definition at line 2067 of file TGraph.cxx.

SaveHistogramAndFunctions()

void TGraph::SaveHistogramAndFunctions ( std::ostream &  out, const char *  varname, Int_t &  frameNumber, Option_t *  option  )

protected

Save histogram and list of functions of TGraph as C++ statement Used in all TGraph-derived classes.

Definition at line 2173 of file TGraph.cxx.

SavePrimitive()

void TGraph::SavePrimitive ( std::ostream &  out, Option_t *  option = ""  )

overridevirtual

Save primitive as a C++ statement(s) on output stream out.

Reimplemented from TObject.

Reimplemented in TGraphAsymmErrors, TGraphBentErrors, TGraphErrors, and TGraphMultiErrors.

Definition at line 2119 of file TGraph.cxx.

Scale()

void TGraph::Scale ( Double_t  c1 = 1., Option_t *  option = "y"  )

virtual

Multiply the values of a TGraph by a constant c1.

If option contains "x" the x values are scaled If option contains "y" the y values are scaled If option contains "xy" both x and y values are scaled

Reimplemented in TGraphAsymmErrors, TGraphBentErrors, TGraphErrors, and TGraphMultiErrors.

Definition at line 2232 of file TGraph.cxx.

Set()

void TGraph::Set ( Int_t  n )

virtual

Set number of points in the graph Existing coordinates are preserved New coordinates above fNpoints are preset to 0.

Definition at line 2250 of file TGraph.cxx.

SetEditable()

void TGraph::SetEditable ( Bool_t  editable = kTRUE )

virtual

if editable=kFALSE, the graph cannot be modified with the mouse by default a TGraph is editable

Definition at line 2274 of file TGraph.cxx.

SetHighlight()

void TGraph::SetHighlight ( Bool_t  set = kTRUE )

virtual

Set highlight (enable/disble) mode for the graph by default highlight mode is disable.

Definition at line 2284 of file TGraph.cxx.

SetHistogram()

virtual void TGraph::SetHistogram ( TH1F *  h )

inlinevirtual

Definition at line 184 of file TGraph.h.

SetMaximum()

void TGraph::SetMaximum ( Double_t  maximum = -1111 )

virtual

Set the maximum of the graph.

Reimplemented in TGraphPolar.

Definition at line 2297 of file TGraph.cxx.

SetMinimum()

void TGraph::SetMinimum ( Double_t  minimum = -1111 )

virtual

Set the minimum of the graph.

Reimplemented in TGraphPolar.

Definition at line 2306 of file TGraph.cxx.

SetName()

void TGraph::SetName ( const char *  name = "" )

overridevirtual

Set graph name.

Reimplemented from TNamed.

Definition at line 2354 of file TGraph.cxx.

SetNameTitle()

void TGraph::SetNameTitle ( const char *  name = "", const char *  title = ""  )

overridevirtual

Set graph name and title.

Reimplemented from TNamed.

Definition at line 2390 of file TGraph.cxx.

SetPoint()

void TGraph::SetPoint ( Int_t  i, Double_t  x, Double_t  y  )

virtual

Set x and y values for point number i.

Definition at line 2315 of file TGraph.cxx.

SetPointX()

void TGraph::SetPointX ( Int_t  i, Double_t  x  )

virtual

Set x value for point i.

Definition at line 2339 of file TGraph.cxx.

SetPointY()

void TGraph::SetPointY ( Int_t  i, Double_t  y  )

virtual

Set y value for point i.

Definition at line 2347 of file TGraph.cxx.

SetStats()

void TGraph::SetStats ( Bool_t  stats = kTRUE )

virtual

Set statistics option on/off.

By default, the statistics box is drawn. The paint options can be selected via gStyle->SetOptStat. This function sets/resets the kNoStats bit in the graph object. It has priority over the Style option.

Definition at line 2404 of file TGraph.cxx.

SetTitle()

void TGraph::SetTitle ( const char *  title = "" )

overridevirtual

Change (i.e.

set) the title

if title is in the form stringt;stringx;stringy;stringz the graph title is set to stringt, the x axis title to stringx, the y axis title to stringy, and the z axis title to stringz.

To insert the character ; in one of the titles, one should use #; or #semicolon.

Reimplemented from TNamed.

Definition at line 2370 of file TGraph.cxx.

ShrinkAndCopy()

Double_t ** TGraph::ShrinkAndCopy ( Int_t  size, Int_t  oend  )

protected

if size*2 <= fMaxSize allocate new arrays of size points, copy points [0,oend).

Return newarray (passed or new instance if it was zero and allocations are needed)

Definition at line 2426 of file TGraph.cxx.

Sort()

void TGraph::Sort ( Bool_t(*)(const TGraph *, Int_t, Int_t)  greaterfunc = &TGraph::CompareX, Bool_t  ascending = kTRUE, Int_t  low = 0, Int_t  high = -1111  )

virtual

Sorts the points of this TGraph using in-place quicksort (see e.g.

older glibc). To compare two points the function parameter greaterfunc is used (see TGraph::CompareX for an example of such a method, which is also the default comparison function for Sort). After the sort, greaterfunc(this, i, j) will return kTRUE for all i>j if ascending == kTRUE, and kFALSE otherwise.

The last two parameters are used for the recursive quick sort, stating the range to be sorted

Examples:

// sort points along x axis
graph->Sort();
// sort points along their distance to origin
graph->Sort(&TGraph::CompareRadius);
 
Bool_t CompareErrors(const TGraph* gr, Int_t i, Int_t j) {
  const TGraphErrors* ge=(const TGraphErrors*)gr;
  return (ge->GetEY()[i]>ge->GetEY()[j]); }
// sort using the above comparison function, largest errors first
graph->Sort(&CompareErrors, kFALSE);

Definition at line 2459 of file TGraph.cxx.

Streamer()

void TGraph::Streamer ( TBuffer &  b )

overridevirtual

Stream an object of class TGraph.

Reimplemented from TObject.

Reimplemented in TGraphPolar, TGraphQQ, TGraphAsymmErrors, TGraphBentErrors, TGraphErrors, and TGraphMultiErrors.

Definition at line 2489 of file TGraph.cxx.

StreamerNVirtual()

void TGraph::StreamerNVirtual ( TBuffer &  ClassDef_StreamerNVirtual_b )

inline

Definition at line 200 of file TGraph.h.

SwapPoints()

void TGraph::SwapPoints ( Int_t  pos1, Int_t  pos2  )

protectedvirtual

Swap points.

Reimplemented in TGraphAsymmErrors, TGraphBentErrors, TGraphErrors, and TGraphMultiErrors.

Definition at line 2556 of file TGraph.cxx.

SwapValues()

void TGraph::SwapValues ( Double_t *  arr, Int_t  pos1, Int_t  pos2  )

staticprotected

Swap values.

Definition at line 2584 of file TGraph.cxx.

UpdateArrays()

void TGraph::UpdateArrays ( const std::vector< Int_t > &  sorting_indices, Int_t  numSortedPoints, Int_t  low  )

protectedvirtual

Update the fX and fY arrays with the sorted values.

Reimplemented in TGraphAsymmErrors, TGraphBentErrors, TGraphErrors, and TGraphMultiErrors.

Definition at line 2565 of file TGraph.cxx.

UseCurrentStyle()

void TGraph::UseCurrentStyle ( )

overridevirtual

Set current style settings in this graph This function is called when either TCanvas::UseCurrentStyle or TROOT::ForceStyle have been invoked.

Reimplemented from TObject.

Definition at line 2596 of file TGraph.cxx.

Zero()

void TGraph::Zero	(	Int_t &	k,
		Double_t	AZ,
		Double_t	BZ,
		Double_t	E2,
		Double_t &	X,
		Double_t &	Y,
		Int_t	maxiterations
	)

Find zero of a continuous function.

This function finds a real zero of the continuous real function Y(X) in a given interval (A,B). See accompanying notes for details of the argument list and calling sequence

Definition at line 2690 of file TGraph.cxx.

Member Data Documentation

fFunctions

TList* TGraph::fFunctions

protected

Pointer to list of functions (fits and user)

Definition at line 49 of file TGraph.h.

fHistogram

TH1F* TGraph::fHistogram

protected

Pointer to histogram used for drawing axis.

Definition at line 50 of file TGraph.h.

fMaximum

Double_t TGraph::fMaximum

protected

Maximum value for plotting along y.

Definition at line 52 of file TGraph.h.

fMaxSize

Int_t TGraph::fMaxSize

protected

!Current dimension of arrays fX and fY

Definition at line 45 of file TGraph.h.

fMinimum

Double_t TGraph::fMinimum

protected

Minimum value for plotting along y.

Definition at line 51 of file TGraph.h.

fNpoints

Int_t TGraph::fNpoints

protected

Number of points <= fMaxSize.

Definition at line 46 of file TGraph.h.

fX

Double_t* TGraph::fX

protected

[fNpoints] array of X points

Definition at line 47 of file TGraph.h.

fY

Double_t* TGraph::fY

protected

[fNpoints] array of Y points

Definition at line 48 of file TGraph.h.

Libraries for TGraph:

---

The documentation for this class was generated from the following files:

• hist/hist/inc/TGraph.h
• hist/hist/src/TGraph.cxx