A Graph is a graphics 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.

The picture below gives an example:

{
   TCanvas *c1 = new TCanvas("c1","A Simple Graph Example",200,10,700,500);
   Double_t x[100], y[100];
   Int_t n = 20;
   for (Int_t i=0;i<n;i++) {
     x[i] = i*0.1;
     y[i] = 10*sin(x[i]+0.2);
   }
   TGraph* gr = new TGraph(n,x,y);
   gr->Draw("AC*");
}

Definition at line 41 of file TGraph.h.

Public Types
enum	EStatusBits { kClipFrame = BIT(10), kResetHisto = BIT(17), kNotEditable = BIT(18), kIsSortedX = BIT(19) }

Public Types inherited from TObject
enum	{ kIsOnHeap = 0x01000000, kNotDeleted = 0x02000000, kZombie = 0x04000000, kInconsistent = 0x08000000, kBitMask = 0x00ffffff }

enum	{ kSingleKey = BIT(0), kOverwrite = BIT(1), kWriteDelete = BIT(2) }

enum	EDeprecatedStatusBits { kObjInCanvas = BIT(3) }

enum	EStatusBits { kCanDelete = BIT(0), kMustCleanup = BIT(3), kIsReferenced = BIT(4), kHasUUID = BIT(5), kCannotPick = BIT(6), kNoContextMenu = BIT(8), kInvalidObject = BIT(13) }

Public Member Functions
	TGraph ()
	Graph default constructor. More...

	TGraph (Int_t n)
	Constructor with only the number of points set the arrays x and y will be set later. More...

	TGraph (Int_t n, const Int_t x, const Int_t y)
	Graph normal constructor with ints. More...

	TGraph (Int_t n, const Float_t x, const Float_t y)
	Graph normal constructor with floats. More...

	TGraph (Int_t n, const Double_t x, const Double_t y)
	Graph normal constructor with doubles. More...

	TGraph (const TGraph &gr)
	Copy constructor for this graph. More...

	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. More...

	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. More...

	TGraph (const TH1 *h)
	Graph constructor importing its parameters from the TH1 object passed as argument. More...

	TGraph (const TF1 f, Option_t option="")
	Graph constructor importing its parameters from the TF1 object passed as argument. More...

	TGraph (const char filename, const char format="%lg %lg", Option_t *option="")
	Graph constructor reading input from filename. More...

virtual	~TGraph ()
	Graph default destructor. More...

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. More...

virtual void	Browse (TBrowser *b)
	Browse. More...

virtual Double_t	Chisquare (TF1 f1, Option_t option="") const
	Return the chisquare of this graph with respect to f1. More...

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. More...

virtual Int_t	DistancetoPrimitive (Int_t px, Int_t py)
	Compute distance from point px,py to a graph. More...

virtual void	Draw (Option_t *chopt="")
	Draw this graph with its current attributes. More...

virtual void	DrawGraph (Int_t n, const Int_t x, const Int_t y, Option_t *option="")
	Draw this graph with new attributes. More...

virtual void	DrawGraph (Int_t n, const Float_t x, const Float_t y, Option_t *option="")
	Draw this graph with new attributes. More...

virtual void	DrawGraph (Int_t n, const Double_t x=0, const Double_t y=0, Option_t *option="")
	Draw this graph with new attributes. More...

virtual void	DrawPanel ()
	Display a panel with all graph drawing options. More...

virtual Double_t	Eval (Double_t x, TSpline spline=0, Option_t option="") const
	Interpolate points in this graph at x using a TSpline. More...

virtual void	ExecuteEvent (Int_t event, Int_t px, Int_t py)
	Execute action corresponding to one event. More...

virtual void	Expand (Int_t newsize)
	If array sizes <= newsize, expand storage to 2*newsize. More...

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. More...

virtual TObject *	FindObject (const char *name) const
	Search object named name in the list of functions. More...

virtual TObject *	FindObject (const TObject *obj) const
	Search object obj in the list of functions. More...

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. More...

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. More...

virtual void	FitPanel ()
	Display a GUI panel with all graph fit options. More...

virtual Double_t	GetCorrelationFactor () const
	Return graph correlation factor. More...

virtual Double_t	GetCovariance () const
	Return covariance of vectors x,y. More...

Bool_t	GetEditable () const
	Return kTRUE if kNotEditable bit is not set, kFALSE otherwise. More...

virtual Double_t	GetErrorX (Int_t bin) const
	This function is called by GraphFitChisquare. More...

virtual Double_t	GetErrorXhigh (Int_t bin) const
	This function is called by GraphFitChisquare. More...

virtual Double_t	GetErrorXlow (Int_t bin) const
	This function is called by GraphFitChisquare. More...

virtual Double_t	GetErrorY (Int_t bin) const
	This function is called by GraphFitChisquare. More...

virtual Double_t	GetErrorYhigh (Int_t bin) const
	This function is called by GraphFitChisquare. More...

virtual Double_t	GetErrorYlow (Int_t bin) const
	This function is called by GraphFitChisquare. More...

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. More...

TH1F *	GetHistogram () const
	Returns a pointer to the histogram used to draw the axis Takes into account the two following cases. More...

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) More...

Double_t	GetMinimum () const

Int_t	GetN () const

virtual Int_t	GetPoint (Int_t i, Double_t &x, Double_t &y) const
	Get x and y values for point number i. More...

virtual Double_t	GetRMS (Int_t axis=1) const
	Return RMS of X (axis=1) or Y (axis=2) More...

Double_t *	GetX () const

TAxis *	GetXaxis () const
	Get x axis of the graph. More...

Double_t *	GetY () const

TAxis *	GetYaxis () const
	Get y axis of the graph. More...

virtual void	InitExpo (Double_t xmin=0, Double_t xmax=0)
	Compute Initial values of parameters for an exponential. More...

virtual void	InitGaus (Double_t xmin=0, Double_t xmax=0)
	Compute Initial values of parameters for a gaussian. More...

virtual void	InitPolynom (Double_t xmin=0, Double_t xmax=0)
	Compute Initial values of parameters for a polynom. More...

virtual Int_t	InsertPoint ()
	Insert a new point at the mouse position. More...

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`. More...

virtual Double_t	Integral (Int_t first=0, Int_t last=-1) const
	Integrate the TGraph data within a given (index) range. More...

virtual Bool_t	IsEditable () 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. More...

virtual void	LeastSquareFit (Int_t m, Double_t *a, Double_t xmin=0, Double_t xmax=0)
	Least squares polynomial fitting without weights. More...

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. More...

virtual Int_t	Merge (TCollection *list)
	Adds all graphs from the collection to this graph. More...

TGraph &	operator= (const TGraph &)
	Equal operator for this graph. More...

virtual void	Paint (Option_t *chopt="")
	Draw this graph with its current attributes. More...

void	PaintGraph (Int_t npoints, const Double_t x, const Double_t y, Option_t *chopt)
	Draw the (x,y) as a graph. More...

void	PaintGrapHist (Int_t npoints, const Double_t x, const Double_t y, Option_t *chopt)
	Draw the (x,y) as a histogram. More...

virtual void	PaintStats (TF1 *fit)
	Draw the stats. More...

virtual void	Print (Option_t *chopt="") const
	Print graph values. More...

virtual void	RecursiveRemove (TObject *obj)
	Recursively remove object from the list of functions. More...

virtual Int_t	RemovePoint ()
	Delete point close to the mouse position. More...

virtual Int_t	RemovePoint (Int_t ipoint)
	Delete point number ipoint. More...

virtual void	SavePrimitive (std::ostream &out, Option_t *option="")
	Save primitive as a C++ statement(s) on output stream out. More...

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. More...

virtual void	SetEditable (Bool_t editable=kTRUE)
	if editable=kFALSE, the graph cannot be modified with the mouse by default a TGraph is editable More...

virtual void	SetHistogram (TH1F *h)

virtual void	SetMaximum (Double_t maximum=-1111)
	Set the maximum of the graph. More...

virtual void	SetMinimum (Double_t minimum=-1111)
	Set the minimum of the graph. More...

virtual void	SetPoint (Int_t i, Double_t x, Double_t y)
	Set x and y values for point number i. More...

virtual void	SetTitle (const char *title="")
	Set graph title. More...

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. More...

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

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. More...

Public Member Functions inherited from TNamed
	TNamed ()

	TNamed (const char name, const char title)

	TNamed (const TString &name, const TString &title)

	TNamed (const TNamed &named)
	TNamed copy ctor. More...

virtual	~TNamed ()
	TNamed destructor. More...

virtual void	Clear (Option_t *option="")
	Set name and title to empty strings (""). More...

virtual TObject *	Clone (const char *newname="") const
	Make a clone of an object using the Streamer facility. More...

virtual Int_t	Compare (const TObject *obj) const
	Compare two TNamed objects. More...

virtual void	Copy (TObject &named) const
	Copy this to obj. More...

virtual void	FillBuffer (char *&buffer)
	Encode TNamed into output buffer. More...

virtual const char *	GetName () const
	Returns name of object. More...

virtual const char *	GetTitle () const
	Returns title of object. More...

virtual ULong_t	Hash () const
	Return hash value for this object. More...

virtual Bool_t	IsSortable () const

virtual void	ls (Option_t *option="") const
	List TNamed name and title. More...

TNamed &	operator= (const TNamed &rhs)
	TNamed assignment operator. More...

virtual void	SetName (const char *name)
	Set the name of the TNamed. More...

virtual void	SetNameTitle (const char name, const char title)
	Set all the TNamed parameters (name and title). More...

virtual Int_t	Sizeof () const
	Return size of the TNamed part of the TObject. More...

Public Member Functions inherited from TObject
	TObject ()
	TObject constructor. More...

	TObject (const TObject &object)
	TObject copy ctor. More...

virtual	~TObject ()
	TObject destructor. More...

void	AbstractMethod (const char *method) const
	Use this method to implement an "abstract" method that you don't want to leave purely abstract. More...

virtual void	AppendPad (Option_t *option="")
	Append graphics object to current pad. More...

ULong_t	CheckedHash ()
	Checked and record whether for this class has a consistent Hash/RecursiveRemove setup (*) and then return the regular Hash value for this object. More...

virtual const char *	ClassName () const
	Returns name of class to which the object belongs. More...

virtual void	Delete (Option_t *option="")
	Delete this object. More...

virtual void	DrawClass () const
	Draw class inheritance tree of the class to which this object belongs. More...

virtual TObject *	DrawClone (Option_t *option="") const
	Draw a clone of this object in the current selected pad for instance with: `gROOT->SetSelectedPad(gPad)`. More...

virtual void	Dump () const
	Dump contents of object on stdout. More...

virtual void	Error (const char method, const char msgfmt,...) const
	Issue error message. More...

virtual void	Execute (const char method, const char params, Int_t *error=0)
	Execute method on this object with the given parameter string, e.g. More...

virtual void	Execute (TMethod method, TObjArray params, Int_t *error=0)
	Execute method on this object with parameters stored in the TObjArray. More...

virtual void	Fatal (const char method, const char msgfmt,...) const
	Issue fatal error message. More...

virtual Option_t *	GetDrawOption () const
	Get option used by the graphics system to draw this object. More...

virtual const char *	GetIconName () const
	Returns mime type name of object. More...

virtual char *	GetObjectInfo (Int_t px, Int_t py) const
	Returns string containing info about the object at position (px,py). More...

virtual Option_t *	GetOption () const

virtual UInt_t	GetUniqueID () const
	Return the unique object id. More...

virtual Bool_t	HandleTimer (TTimer *timer)
	Execute action in response of a timer timing out. More...

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. More...

virtual void	Info (const char method, const char msgfmt,...) const
	Issue info message. More...

virtual Bool_t	InheritsFrom (const char *classname) const
	Returns kTRUE if object inherits from class "classname". More...

virtual Bool_t	InheritsFrom (const TClass *cl) const
	Returns kTRUE if object inherits from TClass cl. More...

virtual void	Inspect () const
	Dump contents of this object in a graphics canvas. More...

void	InvertBit (UInt_t f)

virtual Bool_t	IsEqual (const TObject *obj) const
	Default equal comparison (objects are equal if they have the same address in memory). More...

virtual Bool_t	IsFolder () const
	Returns kTRUE in case object contains browsable objects (like containers or lists of other objects). More...

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). More...

virtual Bool_t	Notify ()
	This method must be overridden to handle object notification. More...

void	Obsolete (const char method, const char asOfVers, const char *removedFromVers) const
	Use this method to declare a method obsolete. More...

void	operator delete (void *ptr)
	Operator delete. More...

void	operator delete[] (void *ptr)
	Operator delete []. More...

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. More...

virtual void	Pop ()
	Pop on object drawn in a pad to the top of the display list. More...

virtual Int_t	Read (const char *name)
	Read contents of object with specified name from the current directory. More...

void	ResetBit (UInt_t f)

virtual void	SaveAs (const char filename="", Option_t option="") const
	Save this object in the file specified by filename. More...

void	SetBit (UInt_t f, Bool_t set)
	Set or unset the user status bits as specified in f. More...

void	SetBit (UInt_t f)

virtual void	SetDrawOption (Option_t *option="")
	Set drawing option for object. More...

virtual void	SetUniqueID (UInt_t uid)
	Set the unique object id. More...

virtual void	SysError (const char method, const char msgfmt,...) const
	Issue system error message. More...

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. More...

virtual Int_t	Write (const char *name=0, Int_t option=0, Int_t bufsize=0)
	Write this object to the current directory. More...

virtual Int_t	Write (const char *name=0, Int_t option=0, Int_t bufsize=0) const
	Write this object to the current directory. More...

Public Member Functions inherited from TAttLine
	TAttLine ()
	AttLine default constructor. More...

	TAttLine (Color_t lcolor, Style_t lstyle, Width_t lwidth)
	AttLine normal constructor. More...

virtual	~TAttLine ()
	AttLine destructor. More...

void	Copy (TAttLine &attline) const
	Copy this line attributes to a new TAttLine. More...

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. More...

virtual Color_t	GetLineColor () const
	Return the line color. More...

virtual Style_t	GetLineStyle () const
	Return the line style. More...

virtual Width_t	GetLineWidth () const
	Return the line width. More...

virtual void	Modify ()
	Change current line attributes if necessary. More...

virtual void	ResetAttLine (Option_t *option="")
	Reset this line attributes to default values. More...

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. More...

virtual void	SetLineAttributes ()
	Invoke the DialogCanvas Line attributes. More...

virtual void	SetLineColor (Color_t lcolor)
	Set the line color. More...

virtual void	SetLineColorAlpha (Color_t lcolor, Float_t lalpha)
	Set a transparent line color. More...

virtual void	SetLineStyle (Style_t lstyle)
	Set the line style. More...

virtual void	SetLineWidth (Width_t lwidth)
	Set the line width. More...

Public Member Functions inherited from TAttFill
	TAttFill ()
	AttFill default constructor. More...

	TAttFill (Color_t fcolor, Style_t fstyle)
	AttFill normal constructor. More...

virtual	~TAttFill ()
	AttFill destructor. More...

void	Copy (TAttFill &attfill) const
	Copy this fill attributes to a new TAttFill. More...

virtual Color_t	GetFillColor () const
	Return the fill area color. More...

virtual Style_t	GetFillStyle () const
	Return the fill area style. More...

virtual Bool_t	IsTransparent () const

virtual void	Modify ()
	Change current fill area attributes if necessary. More...

virtual void	ResetAttFill (Option_t *option="")
	Reset this fill attributes to default values. More...

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. More...

virtual void	SetFillAttributes ()
	Invoke the DialogCanvas Fill attributes. More...

virtual void	SetFillColor (Color_t fcolor)
	Set the fill area color. More...

virtual void	SetFillColorAlpha (Color_t fcolor, Float_t falpha)
	Set a transparent fill color. More...

virtual void	SetFillStyle (Style_t fstyle)
	Set the fill area style. More...

Public Member Functions inherited from TAttMarker
	TAttMarker ()
	TAttMarker default constructor. More...

	TAttMarker (Color_t color, Style_t style, Size_t msize)
	TAttMarker normal constructor. More...

virtual	~TAttMarker ()
	TAttMarker destructor. More...

void	Copy (TAttMarker &attmarker) const
	Copy this marker attributes to a new TAttMarker. More...

virtual Color_t	GetMarkerColor () const
	Return the marker color. More...

virtual Size_t	GetMarkerSize () const
	Return the marker size. More...

virtual Style_t	GetMarkerStyle () const
	Return the marker style. More...

virtual void	Modify ()
	Change current marker attributes if necessary. More...

virtual void	ResetAttMarker (Option_t *toption="")
	Reset this marker attributes to the default values. More...

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. More...

virtual void	SetMarkerAttributes ()
	Invoke the DialogCanvas Marker attributes. More...

virtual void	SetMarkerColor (Color_t mcolor=1)
	Set the marker color. More...

virtual void	SetMarkerColorAlpha (Color_t mcolor, Float_t malpha)
	Set a transparent marker color. More...

virtual void	SetMarkerSize (Size_t msize=1)
	Set the marker size. More...

virtual void	SetMarkerStyle (Style_t mstyle=1)
	Set the marker style. More...

Static Public Member Functions
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". More...

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". More...

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. More...

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. More...

Static Public Member Functions inherited from TObject
static Long_t	GetDtorOnly ()
	Return destructor only flag. More...

static Bool_t	GetObjectStat ()
	Get status of object stat flag. More...

static void	SetDtorOnly (void *obj)
	Set destructor only flag. More...

static void	SetObjectStat (Bool_t stat)
	Turn on/off tracking of objects in the TObjectTable. More...

Protected Member Functions
virtual Double_t **	Allocate (Int_t newsize)

Double_t **	AllocateArrays (Int_t Narrays, Int_t arraySize)
	Allocate arrays. More...

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. More...

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. More...

Bool_t	CtorAllocate ()
	In constructors set fNpoints than call this method. More...

virtual Bool_t	DoMerge (const TGraph *g)
	protected function to perform the merge operation of a graph More...

Double_t **	ExpandAndCopy (Int_t size, Int_t iend)
	if size > fMaxSize allocate new arrays of 2*size points and copy iend first points. More...

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. More...

Double_t **	ShrinkAndCopy (Int_t size, Int_t iend)
	if size*2 <= fMaxSize allocate new arrays of size points, copy points [0,oend). More...

virtual void	SwapPoints (Int_t pos1, Int_t pos2)
	Swap points. More...

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). More...

void	MakeZombie ()

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

Protected Attributes
TList *	fFunctions
	Pointer to list of functions (fits and user) More...

TH1F *	fHistogram
	Pointer to histogram used for drawing axis. More...

Double_t	fMaximum
	Maximum value for plotting along y. More...

Int_t	fMaxSize
	!Current dimension of arrays fX and fY More...

Double_t	fMinimum
	Minimum value for plotting along y. More...

Int_t	fNpoints
	Number of points <= fMaxSize. More...

Double_t *	fX
	[fNpoints] array of X points More...

Double_t *	fY
	[fNpoints] array of Y points More...

Protected Attributes inherited from TNamed
TString	fName

TString	fTitle

Protected Attributes inherited from TAttLine
Color_t	fLineColor
	Line color. More...

Style_t	fLineStyle
	Line style. More...

Width_t	fLineWidth
	Line width. More...

Protected Attributes inherited from TAttFill
Color_t	fFillColor
	Fill area color. More...

Style_t	fFillStyle
	Fill area style. More...

Protected Attributes inherited from TAttMarker
Color_t	fMarkerColor
	Marker color. More...

Size_t	fMarkerSize
	Marker size. More...

Style_t	fMarkerStyle
	Marker style. More...

#include <TGraph.h>

Inheritance diagram for TGraph:

[legend]

Member Enumeration Documentation

◆ EStatusBits

enum TGraph::EStatusBits

Enumerator
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

Definition at line 69 of file TGraph.h.

Constructor & Destructor Documentation

◆ TGraph() [1/11]

TGraph::TGraph ( )

Graph default constructor.

Definition at line 86 of file TGraph.cxx.

◆ TGraph() [2/11]

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 96 of file TGraph.cxx.

◆ TGraph() [3/11]

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

Graph normal constructor with ints.

Definition at line 107 of file TGraph.cxx.

◆ TGraph() [4/11]

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

Graph normal constructor with floats.

Definition at line 125 of file TGraph.cxx.

◆ TGraph() [5/11]

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

Graph normal constructor with doubles.

Definition at line 143 of file TGraph.cxx.

◆ TGraph() [6/11]

TGraph::TGraph ( const TGraph & gr )

Copy constructor for this graph.

Definition at line 160 of file TGraph.cxx.

◆ TGraph() [7/11]

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 248 of file TGraph.cxx.

◆ TGraph() [8/11]

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 267 of file TGraph.cxx.

◆ TGraph() [9/11]

TGraph::TGraph ( const TH1 * h )

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

Definition at line 283 of file TGraph.cxx.

◆ TGraph() [10/11]

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 325 of file TGraph.cxx.

◆ TGraph() [11/11]

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 '' (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 (' ', '', ',', ';') used once (e.g. "1;1") or in a combined way (" 1;,;; 1"). Note in that case, the instantiation is about 2 times slower.

Definition at line 384 of file TGraph.cxx.

◆ ~TGraph()

TGraph::~TGraph ( )

virtual

Graph default destructor.

Definition at line 505 of file TGraph.cxx.

Member Function Documentation

◆ Allocate()

Double_t ** TGraph::Allocate ( Int_t newsize )

inlineprotectedvirtual

Reimplemented in TGraphBentErrors, TGraphAsymmErrors, and TGraphErrors.

Definition at line 182 of file TGraph.h.

◆ AllocateArrays()

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

protected

Allocate arrays.

Definition at line 529 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 TGraphBentErrors, TGraphAsymmErrors, and TGraphErrors.

Definition at line 552 of file TGraph.cxx.

◆ Browse()

void TGraph::Browse ( TBrowser * b )

virtual

Browse.

Reimplemented from TObject.

Definition at line 565 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 591 of file TGraph.cxx.

◆ 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 608 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 636 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 619 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 627 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 TGraphBentErrors, TGraphAsymmErrors, and TGraphErrors.

Definition at line 645 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 TGraphBentErrors, TGraphAsymmErrors, and TGraphErrors.

Definition at line 676 of file TGraph.cxx.

◆ CopyPoints()

Bool_t TGraph::CopyPoints	(	Double_t **	arrays,
		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 TGraphBentErrors, TGraphAsymmErrors, and TGraphErrors.

Definition at line 693 of file TGraph.cxx.

◆ CtorAllocate()

Bool_t TGraph::CtorAllocate ( void )

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 719 of file TGraph.cxx.

◆ DistancetoPrimitive()

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

virtual

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 789 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 TGraphBentErrors, TGraphAsymmErrors, and TGraphErrors.

Definition at line 2428 of file TGraph.cxx.

◆ Draw()

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

virtual

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 745 of file TGraph.cxx.

◆ DrawGraph() [1/3]

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 799 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 812 of file TGraph.cxx.

◆ DrawGraph() [3/3]

void TGraph::DrawGraph	(	Int_t	n,
		const Double_t *	x = `0`,
		const Double_t *	y = `0`,
		Option_t *	option = `""`
	)

virtual

Draw this graph with new attributes.

Definition at line 825 of file TGraph.cxx.

◆ DrawPanel()

void TGraph::DrawPanel ( )

virtual

Display a panel with all graph drawing options.

Definition at line 842 of file TGraph.cxx.

◆ Eval()

Double_t TGraph::Eval	(	Double_t	x,
		TSpline *	spline = `0`,
		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 863 of file TGraph.cxx.

◆ ExecuteEvent()

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

virtual

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 966 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 975 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.

Returns kTRUE if size was altered

Definition at line 986 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 1000 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 TGraphBentErrors, TGraphAsymmErrors, and TGraphErrors.

Definition at line 1014 of file TGraph.cxx.

◆ FindObject() [1/2]

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

virtual

Search object named name in the list of functions.

Reimplemented from TObject.

Definition at line 1023 of file TGraph.cxx.

◆ FindObject() [2/2]

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

virtual

Search object obj in the list of functions.

Reimplemented from TObject.

Definition at line 1032 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.

interface to TGraph::Fit(TF1 *f1...

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.

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 1050 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.

f1 is an already predefined function created by TF1. Predefined functions such as gaus, expo and poln are automatically created by ROOT.

The list of fit options is given in parameter option.

option	description
"W"	Set all weights to 1; ignore error bars
"U"	Use a User specified fitting algorithm (via SetFCN)
"Q"	Quiet mode (minimum printing)
"V"	Verbose mode (default is between Q and V)
"E"	Perform better Errors estimation using Minos technique
"B"	User defined parameter settings are used for predefined functions like "gaus", "expo", "poln", "landau". Use this option when you want to fix one or more parameters for these functions.
"M"	More. Improve fit results. It uses the IMPROVE command of TMinuit (see TMinuit::mnimpr). This algorithm attempts to improve the found local minimum by searching for a better one.
"R"	Use the Range specified in the function range
"N"	Do not store the graphics function, do not draw
"0"	Do not plot the result of the fit. By default the fitted function is drawn unless the option "N" above is specified.
"+"	Add this new fitted function to the list of fitted functions (by default, any previous function is deleted)
"C"	In case of linear fitting, do not calculate the chisquare (saves time)
"F"	If fitting a polN, use the minuit fitter
"EX0"	When fitting a TGraphErrors or TGraphAsymErrors do not consider errors in the coordinate
"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
"S"	The result of the fit is returned in the TFitResultPtr (see below Access to the Fit Result)

When the fit is drawn (by default), the parameter goption may be used to specify a list of graphics options. See TGraphPainter for a complete list of these options.

In order to use the Range option, one must first create a function with the expression to be fitted. For example, if your graph has a defined range between -4 and 4 and you want to fit a gaussian only in the interval 1 to 3, you can do:

   TF1 *f1 = new TF1("f1","gaus",1,3);
   graph->Fit("f1","R");

Who is calling this function:

Note that this function is called when calling TGraphErrors::Fit or TGraphAsymmErrors::Fit ot TGraphBentErrors::Fit See the discussion below on error calculation.

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 "[0]*x + [1]*sin(x)", create a TF1 *f1=new TF1("f1", "x++sin(x)", xmin, xmax); For such a TF1 you don't have to set the initial conditions. Going via the linear fitter for functions, linear in parameters, gives a considerable advantage in speed.

Setting initial conditions:

Parameters must be initialized before invoking the Fit function. The setting of the parameter initial values is automatic for the predefined functions : poln, expo, gaus, landau. One can however disable this automatic computation by specifying the option "B". You can specify boundary limits for some or all parameters via

 f1->SetParLimits(p_number, parmin, parmax);

If parmin>=parmax, the parameter is fixed Note that you are not forced to fix the limits for all parameters. For example, if you fit a function with 6 parameters, you can do:

func->SetParameters(0,3.1,1.e-6,0.1,-8,100); func->SetParLimits(4,-10,-4); func->SetParLimits(5, 1,1); With this setup, parameters 0->3 can vary freely. Parameter 4 has boundaries [-10,-4] with initial value -8. Parameter 5 is fixed to 100.

Fit range:

The fit range can be specified in two ways:

specify rxmax > rxmin (default is rxmin=rxmax=0)
specify the option "R". In this case, the function will be taken instead of the full graph range.

Changing the fitting function:

By default a chi2 fitting function is used for fitting a TGraph. The function is implemented in FitUtil::EvaluateChi2. In case of TGraphErrors an effective chi2 is used (see below TGraphErrors fit) To specify a User defined fitting function, specify option "U" and call the following functions:

TVirtualFitter::Fitter(mygraph)->SetFCN(MyFittingFunction) where MyFittingFunction is of type: extern void MyFittingFunction(Int_t &npar, Double_t *gin, Double_t &f, Double_t *u, Int_t flag);

TGraphErrors fit:

In case of a TGraphErrors object, when x errors are present, the error along x, is projected along the y-direction by calculating the function at the points x-exlow and x+exhigh. The chisquare is then computed as the sum of the quantity below at each 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 function f(x).

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

thanks to Andy Haas (haas@.nosp@m.yaho.nosp@m.o.com) for adding the case with TGraphAsymmErrors University of Washington

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. The improvement, compared to the first method (f(x+ exhigh) - f(x-exlow))/2 is of (error of x)**2 order. This approach is called "effective variance method". This improvement has been made in version 4.00/08 by Anna Kreshuk. The implementation is provided in the function FitUtil::EvaluateChi2Effective

NOTE:

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.
The effective variance technique assumes that there is no correlation between the x and y coordinate.
The standard chi2 (least square) method without error in the coordinates (x) can be forced by using option "EX0"
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, go through minuit (use option "F" for polynomial fitting).
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: errorp *= sqrt(chisquare/(ndf-1))

Access to the fit result

The function returns a TFitResultPtr which can hold a pointer to a TFitResult object. By default the TFitResultPtr contains only the status of the fit which is return by an automatic conversion of the TFitResultPtr to an integer. One can write in this case directly:

Int_t fitStatus =  h->Fit(myFunc)

If the option "S" is instead used, TFitResultPtr contains the TFitResult and behaves as a smart pointer to it. For example one can do:

TFitResultPtr r = h->Fit(myFunc,"S");
TMatrixDSym cov = r->GetCovarianceMatrix();  //  to access the covariance matrix
Double_t chi2   = r->Chi2(); // to retrieve the fit chi2
Double_t par0   = r->Value(0); // retrieve the value for the parameter 0
Double_t err0   = r->ParError(0); // retrieve the error for the parameter 0
r->Print("V");     // print full information of fit including covariance matrix
r->Write();        // store the result in a file

The fit parameters, error and chi2 (but not covariance matrix) can be retrieved also from the fitted function. If the histogram is made persistent, the list of associated functions is also persistent. Given a pointer (see above) to an associated function myfunc, one can retrieve the function/fit parameters with calls such as:

Double_t chi2 = myfunc->GetChisquare();
Double_t par0 = myfunc->GetParameter(0); //value of 1st parameter
Double_t err0 = myfunc->GetParError(0);  //error on first parameter

Access to the fit status

The status of the fit can be obtained converting the TFitResultPtr to an integer independently if the fit option "S" is used or not:

 TFitResultPtr r = h->Fit(myFunc,opt);
 Int_t fitStatus = r;

The fitStatus is 0 if the fit is OK (i.e. no error occurred). The value of the fit status code is negative in case of an error not connected with the minimization procedure, for example when a wrong function is used. Otherwise the return value is the one returned from the minimization procedure. When TMinuit (default case) or Minuit2 are used as minimizer the status returned is : fitStatus = migradResult + 10*minosResult + 100*hesseResult + 1000*improveResult. TMinuit will return 0 (for migrad, minos, hesse or improve) in case of success and 4 in case of error (see the documentation of TMinuit::mnexcm). So for example, for an error only in Minos but not in Migrad a fitStatus of 40 will be returned. Minuit2 will return also 0 in case of success and different values in migrad, minos or hesse depending on the error. See in this case the documentation of Minuit2Minimizer::Minimize for the migradResult, Minuit2Minimizer::GetMinosError for the minosResult and Minuit2Minimizer::Hesse for the hesseResult. If other minimizers are used see their specific documentation for the status code returned. For example in the case of Fumili, for the status returned see TFumili::Minimize.

Associated functions:

One or more object (typically a TF1*) can be added to the list of functions (fFunctions) associated with each graph. When TGraph::Fit is invoked, the fitted function is added to this list. Given a graph gr, one can retrieve an associated function with: TF1 *myfunc = gr->GetFunction("myfunc");

If the graph is made persistent, the list of associated functions is also persistent. Given a pointer (see above) to an associated function myfunc, one can retrieve the function/fit parameters with calls such as:

Double_t chi2 = myfunc->GetChisquare();
Double_t par0 = myfunc->GetParameter(0); //value of 1st parameter
Double_t err0 = myfunc->GetParError(0);  //error on first parameter

Fit Statistics

You can change the statistics box to display the fit parameters with the TStyle::SetOptFit(mode) method. This mode has four digits. mode = pcev (default = 0111)

v = 1;  print name/values of parameters
e = 1;  print errors (if e=1, v must be 1)
c = 1;  print Chisquare/Number of degrees of freedom
p = 1;  print Probability

For example: gStyle->SetOptFit(1011); prints the fit probability, parameter names/values, and errors. You can change the position of the statistics box with these lines (where g is a pointer to the TGraph):

Root > TPaveStats *st = (TPaveStats*)g->GetListOfFunctions()->FindObject("stats")
Root > st->SetX1NDC(newx1); //new x start position
Root > st->SetX2NDC(newx2); //new x end position

Definition at line 1294 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 1309 of file TGraph.cxx.

◆ GetCorrelationFactor()

Double_t TGraph::GetCorrelationFactor ( ) const

virtual

Return graph correlation factor.

Definition at line 1331 of file TGraph.cxx.

◆ GetCovariance()

Double_t TGraph::GetCovariance ( ) const

virtual

Return covariance of vectors x,y.

Definition at line 1343 of file TGraph.cxx.

◆ GetEditable()

Bool_t TGraph::GetEditable ( ) const

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

Definition at line 2148 of file TGraph.cxx.

◆ GetErrorX()

Double_t TGraph::GetErrorX ( Int_t bin ) const

virtual

This function is called by GraphFitChisquare.

It always returns a negative value. Real implementation in TGraphErrors

Reimplemented in TGraphBentErrors, TGraphAsymmErrors, and TGraphErrors.

Definition at line 1397 of file TGraph.cxx.

◆ GetErrorXhigh()

Double_t TGraph::GetErrorXhigh ( Int_t bin ) const

virtual

This function is called by GraphFitChisquare.

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

Reimplemented in TGraphBentErrors, TGraphAsymmErrors, and TGraphErrors.

Definition at line 1416 of file TGraph.cxx.

◆ GetErrorXlow()

Double_t TGraph::GetErrorXlow ( Int_t bin ) const

virtual

This function is called by GraphFitChisquare.

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

Reimplemented in TGraphBentErrors, TGraphAsymmErrors, and TGraphErrors.

Definition at line 1426 of file TGraph.cxx.

◆ GetErrorY()

Double_t TGraph::GetErrorY ( Int_t bin ) const

virtual

This function is called by GraphFitChisquare.

It always returns a negative value. Real implementation in TGraphErrors

Reimplemented in TGraphBentErrors, TGraphAsymmErrors, and TGraphErrors.

Definition at line 1406 of file TGraph.cxx.

◆ GetErrorYhigh()

Double_t TGraph::GetErrorYhigh ( Int_t bin ) const

virtual

This function is called by GraphFitChisquare.

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

Reimplemented in TGraphBentErrors, TGraphAsymmErrors, and TGraphErrors.

Definition at line 1436 of file TGraph.cxx.

◆ GetErrorYlow()

Double_t TGraph::GetErrorYlow ( Int_t bin ) const

virtual

This function is called by GraphFitChisquare.

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

Reimplemented in TGraphBentErrors, TGraphAsymmErrors, and TGraphErrors.

Definition at line 1446 of file TGraph.cxx.

◆ GetEX()

virtual Double_t* TGraph::GetEX ( ) const

inlinevirtual

Reimplemented in TGraphErrors.

Definition at line 131 of file TGraph.h.

◆ GetEXhigh()

virtual Double_t* TGraph::GetEXhigh ( ) const

inlinevirtual

Reimplemented in TGraphBentErrors, and TGraphAsymmErrors.

Definition at line 133 of file TGraph.h.

◆ GetEXhighd()

virtual Double_t* TGraph::GetEXhighd ( ) const

inlinevirtual

Reimplemented in TGraphBentErrors.

Definition at line 138 of file TGraph.h.

◆ GetEXlow()

virtual Double_t* TGraph::GetEXlow ( ) const

inlinevirtual

Reimplemented in TGraphBentErrors, and TGraphAsymmErrors.

Definition at line 134 of file TGraph.h.

◆ GetEXlowd()

virtual Double_t* TGraph::GetEXlowd ( ) const

inlinevirtual

Reimplemented in TGraphBentErrors.

Definition at line 137 of file TGraph.h.

◆ GetEY()

virtual Double_t* TGraph::GetEY ( ) const

inlinevirtual

Reimplemented in TGraphErrors.

Definition at line 132 of file TGraph.h.

◆ GetEYhigh()

virtual Double_t* TGraph::GetEYhigh ( ) const

inlinevirtual

Reimplemented in TGraphBentErrors, and TGraphAsymmErrors.

Definition at line 135 of file TGraph.h.

◆ GetEYhighd()

virtual Double_t* TGraph::GetEYhighd ( ) const

inlinevirtual

Reimplemented in TGraphBentErrors.

Definition at line 140 of file TGraph.h.

◆ GetEYlow()

virtual Double_t* TGraph::GetEYlow ( ) const

inlinevirtual

Reimplemented in TGraphBentErrors, and TGraphAsymmErrors.

Definition at line 136 of file TGraph.h.

◆ GetEYlowd()

virtual Double_t* TGraph::GetEYlowd ( ) const

inlinevirtual

Reimplemented in TGraphBentErrors.

Definition at line 139 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 1457 of file TGraph.cxx.

◆ GetHistogram()

TH1F * TGraph::GetHistogram ( ) const

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

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

Definition at line 1469 of file TGraph.cxx.

◆ GetListOfFunctions()

TList* TGraph::GetListOfFunctions ( ) const

inline

Definition at line 116 of file TGraph.h.

◆ GetMaximum()

Double_t TGraph::GetMaximum ( ) const

inline

Definition at line 141 of file TGraph.h.

◆ GetMaxSize()

Int_t TGraph::GetMaxSize ( ) const

inline

Definition at line 121 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 1359 of file TGraph.cxx.

◆ GetMinimum()

Double_t TGraph::GetMinimum ( ) const

inline

Definition at line 142 of file TGraph.h.

◆ GetN()

Int_t TGraph::GetN ( ) const

inline

Definition at line 122 of file TGraph.h.

◆ 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 1580 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 1374 of file TGraph.cxx.

◆ GetX()

Double_t* TGraph::GetX ( ) const

inline

Definition at line 129 of file TGraph.h.

◆ GetXaxis()

TAxis * TGraph::GetXaxis ( ) const

Get x axis of the graph.

Definition at line 1592 of file TGraph.cxx.

◆ GetY()

Double_t* TGraph::GetY ( ) const

inline

Definition at line 130 of file TGraph.h.

◆ GetYaxis()

TAxis * TGraph::GetYaxis ( ) const

Get y axis of the graph.

Definition at line 1602 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 1650 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 1612 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 1671 of file TGraph.cxx.

◆ InsertPoint()

Int_t TGraph::InsertPoint ( )

virtual

Insert a new point at the mouse position.

Definition at line 1691 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 1736 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

Definition at line 1790 of file TGraph.cxx.

◆ IsEditable()

virtual Bool_t TGraph::IsEditable ( ) const

inlinevirtual

Definition at line 153 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 1823 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]	ma	array of parameters
[in]	mfirst	1st point number to fit (default =0)
[in]	mlast	last point number to fit (default=fNpoints-1)

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

Definition at line 1838 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 1913 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 poins in the result or -1 in case of an error.

Reimplemented in TGraphAsymmErrors, and TGraphErrors.

Definition at line 2411 of file TGraph.cxx.

◆ operator=()

TGraph & TGraph::operator= ( const TGraph & gr )

Equal operator for this graph.

Definition at line 187 of file TGraph.cxx.

◆ Paint()

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

virtual

Draw this graph with its current attributes.

Reimplemented from TObject.

Definition at line 1959 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 1968 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 1977 of file TGraph.cxx.

◆ PaintStats()

void TGraph::PaintStats ( TF1 * fit )

virtual

Draw the stats.

Definition at line 1986 of file TGraph.cxx.

◆ Print()

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

virtual

Print graph values.

Reimplemented from TNamed.

Reimplemented in TGraphBentErrors, TGraphAsymmErrors, TGraphErrors, RooHist, RooCurve, and RooEllipse.

Definition at line 1995 of file TGraph.cxx.

◆ RecursiveRemove()

void TGraph::RecursiveRemove ( TObject * obj )

virtual

Recursively remove object from the list of functions.

Reimplemented from TObject.

Definition at line 2005 of file TGraph.cxx.

◆ RemovePoint() [1/2]

Int_t TGraph::RemovePoint ( )

virtual

Delete point close to the mouse position.

Definition at line 2016 of file TGraph.cxx.

◆ RemovePoint() [2/2]

Int_t TGraph::RemovePoint ( Int_t ipoint )

virtual

Delete point number ipoint.

Definition at line 2039 of file TGraph.cxx.

◆ SavePrimitive()

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

virtual

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

Reimplemented from TObject.

Reimplemented in TGraphBentErrors, TGraphAsymmErrors, TGraphErrors, and TCutG.

Definition at line 2053 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 2133 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 2157 of file TGraph.cxx.

◆ SetHistogram()

virtual void TGraph::SetHistogram ( TH1F * h )

inlinevirtual

Definition at line 168 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 2166 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 2175 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 2184 of file TGraph.cxx.

◆ SetTitle()

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

virtual

Set graph title.

Reimplemented from TNamed.

Definition at line 2208 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 2220 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 2253 of file TGraph.cxx.

◆ SwapPoints()

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

protectedvirtual

Swap points.

Reimplemented in TGraphBentErrors, TGraphAsymmErrors, and TGraphErrors.

Definition at line 2355 of file TGraph.cxx.

◆ SwapValues()

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

staticprotected

Swap values.

Definition at line 2364 of file TGraph.cxx.

◆ UseCurrentStyle()

void TGraph::UseCurrentStyle ( )

virtual

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 2376 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 2443 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:

[legend]

Notes

Public Types

Public Member Functions

Static Public Member Functions

Protected Member Functions

Static Protected Member Functions

Protected Attributes

Member Enumeration Documentation

◆ EStatusBits

Constructor & Destructor Documentation

◆ TGraph() [1/11]

◆ TGraph() [2/11]

◆ TGraph() [3/11]

◆ TGraph() [4/11]

◆ TGraph() [5/11]

◆ TGraph() [6/11]

◆ TGraph() [7/11]

◆ TGraph() [8/11]

◆ TGraph() [9/11]

◆ TGraph() [10/11]

◆ TGraph() [11/11]

◆ ~TGraph()

Member Function Documentation

◆ Allocate()

◆ AllocateArrays()

◆ Apply()

◆ Browse()

◆ Chisquare()

◆ CompareArg()

◆ CompareRadius()

◆ CompareX()

◆ CompareY()

◆ ComputeRange()

◆ CopyAndRelease()

◆ CopyPoints()

◆ CtorAllocate()

◆ DistancetoPrimitive()

◆ DoMerge()

◆ Draw()

◆ DrawGraph() [1/3]

◆ DrawGraph() [2/3]

◆ DrawGraph() [3/3]

◆ DrawPanel()

◆ Eval()

◆ ExecuteEvent()

◆ Expand() [1/2]

◆ Expand() [2/2]

◆ ExpandAndCopy()

◆ FillZero()

◆ FindObject() [1/2]

◆ FindObject() [2/2]

◆ Fit() [1/2]

◆ Fit() [2/2]

Linear fitting:

Setting initial conditions:

Fit range:

Changing the fitting function:

TGraphErrors fit:

Access to the fit result

Access to the fit status

Associated functions:

Fit Statistics

◆ FitPanel()

◆ GetCorrelationFactor()

◆ GetCovariance()

◆ GetEditable()

◆ GetErrorX()

◆ GetErrorXhigh()

◆ GetErrorXlow()

◆ GetErrorY()

◆ GetErrorYhigh()

◆ GetErrorYlow()

◆ GetEX()

◆ GetEXhigh()

◆ GetEXhighd()

◆ GetEXlow()

◆ GetEXlowd()

◆ GetEY()

◆ GetEYhigh()

◆ GetEYhighd()