A TMultiGraph is a collection of TGraph (or derived) objects.

It allows to manipulate a set of graphs as a single entity. In particular, when drawn, the X and Y axis ranges are automatically computed such as all the graphs will be visible.

TMultiGraph::Add should be used to add a new graph to the list.

The TMultiGraph owns the objects in the list.

The drawing options are the same as for TGraph. Like for TGraph, the painting is performed thanks to the TGraphPainter class. All details about the various painting options are given in this class.

Example:

TGraph *gr1 = new TGraph(...
TGraphErrors *gr2 = new TGraphErrors(...
TMultiGraph *mg = new TMultiGraph();
mg->Add(gr1,"lp");
mg->Add(gr2,"cp");
mg->Draw("a");

A special option 3D allows to draw the graphs in a 3D space. See the following example:

{
   auto c0 = new TCanvas("c1","multigraph L3",200,10,700,500);
   auto mg = new TMultiGraph();
   auto gr1 = new TGraph(); gr1->SetLineColor(kBlue);
   auto gr2 = new TGraph(); gr2->SetLineColor(kRed);
   auto gr3 = new TGraph(); gr3->SetLineColor(kGreen);
   auto gr4 = new TGraph(); gr4->SetLineColor(kOrange);
   Double_t dx = 6.28/100;
   Double_t x  = -3.14;
   for (int i=0; i<=100; i++) {
      x = x+dx;
      gr1->SetPoint(i,x,2.*TMath::Sin(x));
      gr2->SetPoint(i,x,TMath::Cos(x));
      gr3->SetPoint(i,x,TMath::Cos(x*x));
      gr4->SetPoint(i,x,TMath::Cos(x*x*x));
   }
   mg->Add(gr4); gr4->SetTitle("Cos(x*x*x)"); gr4->SetLineWidth(3);
   mg->Add(gr3); gr3->SetTitle("Cos(x*x)")  ; gr3->SetLineWidth(3);
   mg->Add(gr2); gr2->SetTitle("Cos(x)")    ; gr2->SetLineWidth(3);
   mg->Add(gr1); gr1->SetTitle("2*Sin(x)")  ; gr1->SetLineWidth(3);
   mg->Draw("a fb l3d");
}

The number of graphs in a multigraph can be retrieve with:

mg->GetListOfGraphs()->GetSize();

The drawing option for each TGraph may be specified as an optional second argument of the Add function.

If a draw option is specified, it will be used to draw the graph, otherwise the graph will be drawn with the option specified in TMultiGraph::Draw.

The following example shows how to fit a TMultiGraph.

{
   auto c1 = new TCanvas("c1","c1",600,400);
   Double_t px1[2] = {2.,4.};
   Double_t dx1[2] = {0.1,0.1};
   Double_t py1[2] = {2.1,4.0};
   Double_t dy1[2] = {0.3,0.2};
   Double_t px2[2] = {3.,5.};
   Double_t dx2[2] = {0.1,0.1};
   Double_t py2[2] = {3.2,4.8};
   Double_t dy2[2] = {0.3,0.2};
   gStyle->SetOptFit(0001);
   auto g1 = new TGraphErrors(2,px1,py1,dx1,dy1);
   g1->SetMarkerStyle(21);
   g1->SetMarkerColor(2);
   auto g2 = new TGraphErrors(2,px2,py2,dx2,dy2);
   g2->SetMarkerStyle(22);
   g2->SetMarkerColor(3);
   auto g = new TMultiGraph();
   g->Add(g1);
   g->Add(g2);
   g->Draw("AP");
   g->Fit("pol1","FQ");
}

The axis titles can be modified the following way:

[...]
auto mg = new TMultiGraph;
mg->SetTitle("title;xaxis title; yaxis title");
mg->Add(g1);
mg->Add(g2);
mg->Draw("apl");

When the graphs in a TMultiGraph are fitted, the fit parameters boxes overlap. The following example shows how to make them all visible.

void multigraph()
{
   gStyle->SetOptFit();
   auto c1 = new TCanvas("c1","multigraph",700,500);
   c1->SetGrid();
   // draw a frame to define the range
   auto mg = new TMultiGraph();
   // create first graph
   const Int_t n1 = 10;
   Double_t px1[] = {-0.1, 0.05, 0.25, 0.35, 0.5, 0.61,0.7,0.85,0.89,0.95};
   Double_t py1[] = {-1,2.9,5.6,7.4,9,9.6,8.7,6.3,4.5,1};
   Double_t ex1[] = {.05,.1,.07,.07,.04,.05,.06,.07,.08,.05};
   Double_t ey1[] = {.8,.7,.6,.5,.4,.4,.5,.6,.7,.8};
   auto gr1 = new TGraphErrors(n1,px1,py1,ex1,ey1);
   gr1->SetMarkerColor(kBlue);
   gr1->SetMarkerStyle(21);
   gr1->Fit("pol6","q");
   mg->Add(gr1);
   // create second graph
   const Int_t n2 = 10;
   Float_t x2[]  = {-0.28, 0.005, 0.19, 0.29, 0.45, 0.56,0.65,0.80,0.90,1.01};
   Float_t y2[]  = {2.1,3.86,7,9,10,10.55,9.64,7.26,5.42,2};
   Float_t ex2[] = {.04,.12,.08,.06,.05,.04,.07,.06,.08,.04};
   Float_t ey2[] = {.6,.8,.7,.4,.3,.3,.4,.5,.6,.7};
   auto gr2 = new TGraphErrors(n2,x2,y2,ex2,ey2);
   gr2->SetMarkerColor(kRed);
   gr2->SetMarkerStyle(20);
   gr2->Fit("pol5","q");
   mg->Add(gr2);
   mg->Draw("ap");
   //force drawing of canvas to generate the fit TPaveStats
   c1->Update();
   auto stats1 = (TPaveStats*)gr1->GetListOfFunctions()->FindObject("stats");
   auto stats2 = (TPaveStats*)gr2->GetListOfFunctions()->FindObject("stats");
   stats1->SetTextColor(kBlue);
   stats2->SetTextColor(kRed);
   stats1->SetX1NDC(0.12); stats1->SetX2NDC(0.32); stats1->SetY1NDC(0.75);
   stats2->SetX1NDC(0.72); stats2->SetX2NDC(0.92); stats2->SetY1NDC(0.78);
   c1->Modified();
}

The axis limits can be changed the like for TGraph. The same methods apply on the multigraph. Note the two differents ways to change limits on X and Y axis.

{
   auto c2 = new TCanvas("c2","c2",600,400);
   TGraph *g[3];
   Double_t x[10] = {0,1,2,3,4,5,6,7,8,9};
   Double_t y[10] = {1,2,3,4,5,5,4,3,2,1};
   auto mg = new TMultiGraph();
   for (int i=0; i<3; i++) {
      g[i] = new TGraph(10, x, y);
      g[i]->SetMarkerStyle(20);
      g[i]->SetMarkerColor(i+2);
      for (int j=0; j<10; j++) y[j] = y[j]-1;
      mg->Add(g[i]);
   }
   mg->Draw("APL");
   mg->GetXaxis()->SetTitle("E_{#gamma} (GeV)");
   mg->GetYaxis()->SetTitle("Coefficients");
   // Change the axis limits
   gPad->Modified();
   mg->GetXaxis()->SetLimits(1.5,7.5);
   mg->SetMinimum(0.);
   mg->SetMaximum(10.);
}

The method TPad::BuildLegend is able to extract the graphs inside a multigraph. The following example demonstrate this.

{
   auto c3 = new TCanvas("c3","c3",600, 400);
   auto mg = new TMultiGraph("mg","mg");
   const Int_t size = 10;
   double px[size];
   double py1[size];
   double py2[size];
   double py3[size];
   for ( int i = 0; i <  size ; ++i ) {
      px[i] = i;
      py1[i] = size - i;
      py2[i] = size - 0.5 * i;
      py3[i] = size - 0.6 * i;
   }
   auto gr1 = new TGraph( size, px, py1 );
   gr1->SetName("gr1");
   gr1->SetTitle("graph 1");
   gr1->SetMarkerStyle(21);
   gr1->SetDrawOption("AP");
   gr1->SetLineColor(2);
   gr1->SetLineWidth(4);
   gr1->SetFillStyle(0);
   auto gr2 = new TGraph( size, px, py2 );
   gr2->SetName("gr2");
   gr2->SetTitle("graph 2");
   gr2->SetMarkerStyle(22);
   gr2->SetMarkerColor(2);
   gr2->SetDrawOption("P");
   gr2->SetLineColor(3);
   gr2->SetLineWidth(4);
   gr2->SetFillStyle(0);
   auto gr3 = new TGraph( size, px, py3 );
   gr3->SetName("gr3");
   gr3->SetTitle("graph 3");
   gr3->SetMarkerStyle(23);
   gr3->SetLineColor(4);
   gr3->SetLineWidth(4);
   gr3->SetFillStyle(0);
   mg->Add( gr1 );
   mg->Add( gr2 );
   gr3->Draw("ALP");
   mg->Draw("LP");
   c3->BuildLegend();
}

Automatic coloring according to the current palette is available as shown in the following example:

void multigraphpalettecolor()
{
   auto mg  = new TMultiGraph();
   auto gr1 = new TGraph(); gr1->SetMarkerStyle(20);
   auto gr2 = new TGraph(); gr2->SetMarkerStyle(21);
   auto gr3 = new TGraph(); gr3->SetMarkerStyle(23);
   auto gr4 = new TGraph(); gr4->SetMarkerStyle(24);
   Double_t dx = 6.28/100;
   Double_t x  = -3.14;
   for (int i=0; i<=100; i++) {
      x = x+dx;
      gr1->SetPoint(i,x,2.*TMath::Sin(x));
      gr2->SetPoint(i,x,TMath::Cos(x));
      gr3->SetPoint(i,x,TMath::Cos(x*x));
      gr4->SetPoint(i,x,TMath::Cos(x*x*x));
   }
   mg->Add(gr4,"PL");
   mg->Add(gr3,"PL");
   mg->Add(gr2,"*L");
   mg->Add(gr1,"PL");
   mg->Draw("A pmc plc");
}

Definition at line 35 of file TMultiGraph.h.

Public Member Functions
	TMultiGraph ()
	TMultiGraph default constructor. More...

	TMultiGraph (const char name, const char title)
	Constructor with name and title. More...

virtual	~TMultiGraph ()
	TMultiGraph destructor. More...

virtual void	Add (TGraph graph, Option_t chopt="")
	Add a new graph to the list of graphs. More...

virtual void	Add (TMultiGraph multigraph, Option_t chopt="")
	Add all the graphs in "multigraph" to the list of graphs. More...

TIter	begin () const
	Get iterator over internal graphs list. More...

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

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

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

TIter	end () const

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 rxmin=0, Axis_t rxmax=0)
	Fit this multigraph with function f1. More...

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

TF1 *	GetFunction (const char *name) const
	Return pointer to function with name. More...

virtual Option_t *	GetGraphDrawOption (const TGraph *gr) const
	Return the draw option for the TGraph `gr` in this TMultiGraph. More...

TH1F *	GetHistogram () const
	Returns a pointer to the histogram used to draw the axis. More...

TList *	GetListOfFunctions ()
	Return pointer to list of functions. More...

const TList *	GetListOfFunctions () const

TList *	GetListOfGraphs () const

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

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

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

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

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

virtual Int_t	IsInside (Double_t x, Double_t y) const
	Return 1 if the point (x,y) is inside one of the graphs 0 otherwise. More...

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

virtual void	LeastSquareLinearFit (Int_t ndata, Double_t &a0, Double_t &a1, Int_t &ifail, Double_t xmin, Double_t xmax)
	Least square linear fit without weights. More...

virtual void	Paint (Option_t *chopt="")
	Paint all the graphs of this multigraph. More...

void	PaintPads (Option_t *chopt="")
	Divides the active pad and draws all Graphs in the Multigraph separately. More...

void	PaintPolyLine3D (Option_t *chopt="")
	Paint all the graphs of this multigraph as 3D lines. More...

virtual void	Print (Option_t *chopt="") const
	Print the list of graphs. More...

virtual void	RecursiveRemove (TObject *obj)
	Recursively remove this object from a list. More...

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

virtual void	SetMaximum (Double_t maximum=-1111)
	Set multigraph maximum. More...

virtual void	SetMinimum (Double_t minimum=-1111)
	Set multigraph minimum. 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 ()

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 void	SetTitle (const char *title="")
	Set the title of the TNamed. 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...

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	ExecuteEvent (Int_t event, Int_t px, Int_t py)
	Execute action corresponding to an event at (px,py). More...

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

virtual TObject *	FindObject (const char *name) const
	Must be redefined in derived classes. More...

virtual TObject *	FindObject (const TObject *obj) const
	Must be redefined in derived classes. 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...

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...

Bool_t	IsOnHeap () const

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...

Bool_t	TestBit (UInt_t f) const

Int_t	TestBits (UInt_t f) const

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

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...

Protected Member Functions
	TMultiGraph (const TMultiGraph &)
	Copy constructor. More...

TMultiGraph &	operator= (const TMultiGraph &)
	Assignment operator. 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 ()

Protected Attributes
TList *	fFunctions

TList *	fGraphs

TH1F *	fHistogram

Double_t	fMaximum

Double_t	fMinimum

Protected Attributes inherited from TNamed
TString	fName

TString	fTitle

Additional Inherited Members
Public Types inherited from TObject
enum	{ kIsOnHeap = 0x01000000, kNotDeleted = 0x02000000, kZombie = 0x04000000, kBitMask = 0x00ffffff }

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

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

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...

#include <TMultiGraph.h>

Inheritance diagram for TMultiGraph:

[legend]

Constructor & Destructor Documentation

◆ TMultiGraph() [1/3]

TMultiGraph::TMultiGraph ( const TMultiGraph & mg )

protected

Copy constructor.

Definition at line 302 of file TMultiGraph.cxx.

◆ TMultiGraph() [2/3]

TMultiGraph::TMultiGraph ( )

TMultiGraph default constructor.

Definition at line 275 of file TMultiGraph.cxx.

◆ TMultiGraph() [3/3]

TMultiGraph::TMultiGraph	(	const char *	name,
		const char *	title
	)

Constructor with name and title.

Definition at line 288 of file TMultiGraph.cxx.

◆ ~TMultiGraph()

TMultiGraph::~TMultiGraph ( )

virtual

TMultiGraph destructor.

Definition at line 333 of file TMultiGraph.cxx.

Member Function Documentation

◆ Add() [1/2]

void TMultiGraph::Add	(	TGraph *	graph,
		Option_t *	chopt = `""`
	)

virtual

Add a new graph to the list of graphs.

Note that the graph is now owned by the TMultigraph. Deleting the TMultiGraph object will automatically delete the graphs. You should not delete the graphs when the TMultigraph is still active.

Definition at line 368 of file TMultiGraph.cxx.

◆ Add() [2/2]

void TMultiGraph::Add	(	TMultiGraph *	multigraph,
		Option_t *	chopt = `""`
	)

virtual

Add all the graphs in "multigraph" to the list of graphs.

If "chopt" is defined all the graphs in "multigraph" will be added with the "chopt" option.
If "chopt" is undefined each graph will be added with the option it had in "multigraph".

Definition at line 384 of file TMultiGraph.cxx.

◆ begin()

TIter TMultiGraph::begin ( ) const

Get iterator over internal graphs list.

Definition at line 1490 of file TMultiGraph.cxx.

◆ Browse()

void TMultiGraph::Browse ( TBrowser * b )

virtual

Browse multigraph.

Reimplemented from TObject.

Definition at line 406 of file TMultiGraph.cxx.

◆ DistancetoPrimitive()

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

virtual

Compute distance from point px,py to each graph.

Reimplemented from TObject.

Definition at line 421 of file TMultiGraph.cxx.

◆ Draw()

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

virtual

Draw this multigraph with its current attributes.

Options to draw a graph are described in TGraphPainter.

The drawing option for each TGraph may be specified as an optional second argument of the Add function. You can use GetGraphDrawOption to return this option.

If a draw option is specified, it will be used to draw the graph, otherwise the graph will be drawn with the option specified in TMultiGraph::Draw. Use GetDrawOption to return the option specified when drawing the TMultiGraph.

Reimplemented from TObject.

Definition at line 458 of file TMultiGraph.cxx.

◆ end()

TIter TMultiGraph::end ( ) const

inline

Definition at line 71 of file TMultiGraph.h.

◆ Fit() [1/2]

TFitResultPtr TMultiGraph::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 TF1::Fit(TF1 *f1...

Definition at line 476 of file TMultiGraph.cxx.

◆ Fit() [2/2]

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

virtual

Fit this multigraph with function f1.

In this function all graphs of the multigraph are fitted simultaneously

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 optionwhich may takes the following values:

"W" Set all errors to 1
"U" Use a User specified fitting algorithm (via SetFCN)
"Q" Quiet mode (minimum printing)
"V" Verbose mode (default is between Q and V)
"B" Use this option when you want to fix one or more parameters and the fitting function is like "gaus","expo","poln","landau".
"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, not calculate the chisquare (saves time)
"F" If fitting a polN, switch to minuit fitter
"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

When the fit is drawn (by default), the parameter goption may be used to specify a list of graphics options. See TGraph::Paint 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 the errors calculation.

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 the TGraphs's. The function is implemented in FitUtil::EvaluateChi2. In case of TGraphErrors an effective chi2 is used (see TGraphErrors fit in TGraph::Fit) and is implemented in FitUtil::EvaluateChi2Effective To specify a User defined fitting function, specify option "U" and call the following function:

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);

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 and it converts automatically to an integer. 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 = graph->Fit("myFunc","S");
TMatrixDSym cov = r->GetCovarianceMatrix();  //  to access the covariance matrix
Double_t par0   = r->Parameter(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.

Associated functions

One or more object (typically a TF1*) can be added to the list of functions (fFunctions) associated to 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 651 of file TMultiGraph.cxx.

◆ FitPanel()

void TMultiGraph::FitPanel ( )

virtual

Display a panel with all histogram fit options.

See class TFitPanel for example

Definition at line 668 of file TMultiGraph.cxx.

◆ GetFunction()

TF1 * TMultiGraph::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 980 of file TMultiGraph.cxx.

◆ GetGraphDrawOption()

Option_t * TMultiGraph::GetGraphDrawOption ( const TGraph * gr ) const

virtual

Return the draw option for the TGraph gr in this TMultiGraph.

The return option is the one specified when calling TMultiGraph::Add(gr,option).

Definition at line 692 of file TMultiGraph.cxx.

◆ GetHistogram()

TH1F * TMultiGraph::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 TMultiGraph::Draw. Return fHistogram
user had called TPad::DrawFrame. return pointer to hframe histogram

Definition at line 962 of file TMultiGraph.cxx.

◆ GetListOfFunctions() [1/2]

TList * TMultiGraph::GetListOfFunctions ( )

Return pointer to list of functions.

If pointer is null create the list

Definition at line 990 of file TMultiGraph.cxx.

◆ GetListOfFunctions() [2/2]

const TList* TMultiGraph::GetListOfFunctions ( ) const

inline

Definition at line 73 of file TMultiGraph.h.

◆ GetListOfGraphs()

TList* TMultiGraph::GetListOfGraphs ( ) const

inline

Definition at line 69 of file TMultiGraph.h.

◆ GetXaxis()

TAxis * TMultiGraph::GetXaxis ( ) const

Get x axis of the graph.

This method returns a valid axis only after the TMultigraph has been drawn.

Definition at line 1001 of file TMultiGraph.cxx.

◆ GetYaxis()

TAxis * TMultiGraph::GetYaxis ( ) const

Get y axis of the graph.

This method returns a valid axis only after the TMultigraph has been drawn.

Definition at line 1014 of file TMultiGraph.cxx.

◆ InitExpo()

void TMultiGraph::InitExpo	(	Double_t	xmin,
		Double_t	xmax
	)

virtual

Compute Initial values of parameters for an exponential.

Definition at line 752 of file TMultiGraph.cxx.

◆ InitGaus()

void TMultiGraph::InitGaus	(	Double_t	xmin,
		Double_t	xmax
	)

virtual

Compute Initial values of parameters for a gaussian.

Definition at line 707 of file TMultiGraph.cxx.

◆ InitPolynom()

void TMultiGraph::InitPolynom	(	Double_t	xmin,
		Double_t	xmax
	)

virtual

Compute Initial values of parameters for a polynom.

Definition at line 769 of file TMultiGraph.cxx.

◆ IsInside()

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

virtual

Return 1 if the point (x,y) is inside one of the graphs 0 otherwise.

Definition at line 941 of file TMultiGraph.cxx.

◆ LeastSquareFit()

void TMultiGraph::LeastSquareFit	(	Int_t	m,
		Double_t *	a,
		Double_t	xmin,
		Double_t	xmax
	)

virtual

Least squares lpolynomial fitting without weights.

m number of parameters
a array of parameters
first 1st point number to fit (default =0)
last last point number to fit (default=fNpoints-1)

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

Definition at line 793 of file TMultiGraph.cxx.

◆ LeastSquareLinearFit()

void TMultiGraph::LeastSquareLinearFit	(	Int_t	ndata,
		Double_t &	a0,
		Double_t &	a1,
		Int_t &	ifail,
		Double_t	xmin,
		Double_t	xmax
	)

virtual

Least square linear fit without weights.

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

ndata: number of points to fit
first: first point number to fit
last: last point to fit O(ndata should be last-first
ifail: return parameter indicating the status of the fit (ifail=0, fit is OK)

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

Definition at line 888 of file TMultiGraph.cxx.

◆ operator=()

TMultiGraph & TMultiGraph::operator= ( const TMultiGraph & mg )

protected

Assignment operator.

Definition at line 316 of file TMultiGraph.cxx.

◆ Paint()

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

virtual

Paint all the graphs of this multigraph.

Reimplemented from TObject.

Definition at line 1026 of file TMultiGraph.cxx.

◆ PaintPads()

void TMultiGraph::PaintPads ( Option_t * chopt = "" )

Divides the active pad and draws all Graphs in the Multigraph separately.

Definition at line 1274 of file TMultiGraph.cxx.

◆ PaintPolyLine3D()

void TMultiGraph::PaintPolyLine3D ( Option_t * chopt = "" )

Paint all the graphs of this multigraph as 3D lines.

Definition at line 1323 of file TMultiGraph.cxx.

◆ Print()

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

virtual

Print the list of graphs.

Reimplemented from TNamed.

Definition at line 1402 of file TMultiGraph.cxx.

◆ RecursiveRemove()

void TMultiGraph::RecursiveRemove ( TObject * obj )

virtual

Recursively remove this object from a list.

Typically implemented by classes that can contain multiple references to a same object.

Reimplemented from TObject.

Definition at line 1418 of file TMultiGraph.cxx.

◆ SavePrimitive()

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

virtual

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

Reimplemented from TObject.

Definition at line 1431 of file TMultiGraph.cxx.

◆ SetMaximum()

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

virtual

Set multigraph maximum.

Definition at line 1471 of file TMultiGraph.cxx.

◆ SetMinimum()

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

virtual

Set multigraph minimum.

Definition at line 1481 of file TMultiGraph.cxx.

Member Data Documentation

◆ fFunctions

TList* TMultiGraph::fFunctions

protected

Definition at line 39 of file TMultiGraph.h.

◆ fGraphs

TList* TMultiGraph::fGraphs

protected

Definition at line 38 of file TMultiGraph.h.

◆ fHistogram

TH1F* TMultiGraph::fHistogram

protected

Definition at line 40 of file TMultiGraph.h.

◆ fMaximum

Double_t TMultiGraph::fMaximum

protected

Definition at line 41 of file TMultiGraph.h.

◆ fMinimum

Double_t TMultiGraph::fMinimum

protected

Definition at line 42 of file TMultiGraph.h.

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

hist/hist/inc/TMultiGraph.h
hist/hist/src/TMultiGraph.cxx

Public Member Functions

Protected Member Functions

Protected Attributes

Additional Inherited Members

Constructor & Destructor Documentation

◆ TMultiGraph() [1/3]

◆ TMultiGraph() [2/3]

◆ TMultiGraph() [3/3]

◆ ~TMultiGraph()

Member Function Documentation

◆ Add() [1/2]

◆ Add() [2/2]

◆ begin()

◆ Browse()

◆ DistancetoPrimitive()

◆ Draw()

◆ end()

◆ Fit() [1/2]

◆ Fit() [2/2]

Who is calling this function ?

Setting initial conditions

Fit range

Changing the fitting function

Access to the fit result

Associated functions

Fit Statistics

◆ FitPanel()

◆ GetFunction()

◆ GetGraphDrawOption()

◆ GetHistogram()

◆ GetListOfFunctions() [1/2]

◆ GetListOfFunctions() [2/2]

◆ GetListOfGraphs()

◆ GetXaxis()

◆ GetYaxis()

◆ InitExpo()

◆ InitGaus()

◆ InitPolynom()

◆ IsInside()

◆ LeastSquareFit()

◆ LeastSquareLinearFit()

◆ operator=()

◆ Paint()

◆ PaintPads()

◆ PaintPolyLine3D()

◆ Print()

◆ RecursiveRemove()

◆ SavePrimitive()

◆ SetMaximum()

◆ SetMinimum()

Member Data Documentation

◆ fFunctions

◆ fGraphs

◆ fHistogram

◆ fMaximum

◆ fMinimum