TMultiGraph Class Reference

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

• Introduction
• MultiGraphs' drawing
  • Setting drawing options
  • Titles setting
  • The option "3D"
  • Legend drawing
  • Automatic coloring
  • Reverse axis
• MultiGraphs' fitting
  • Fit box position
• Axis' limits setting

Introduction

A TMultiGraph 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 number of graphs in a multigraph can be retrieve with:

mg->GetListOfGraphs()->GetEntries();

MultiGraphs' Drawing

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");

Setting drawing options

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

Titles setting

The global title and 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");

The option "3D"

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 = 6.28/1000;
   Double_t x  = -3.14;
 
   for (int i=0; i<=1000; 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->SetTitle("Multi-graph Title; X-axis Title; Y-axis Title");
 
   mg->Draw("a fb l3d");
 
   mg->GetHistogram()->GetXaxis()->SetRangeUser(0.,2.5);
   gPad->Modified();
   gPad->Update();
}

Legend drawing

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

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");
}

Reverse axis

Since

ROOT version 6.19/02

When a TMultiGraph is drawn, the X-axis is drawn with increasing values from left to right and the Y-axis from bottom to top. The two options RX and RY allow to change this order. The option RX allows to draw the X-axis with increasing values from right to left and the RY option allows to draw the Y-axis with increasing values from top to bottom. The following example illustrate how to use these options.

{
   auto *c = new TCanvas();
   c->Divide(2,1);
 
   auto *g1 = new TGraphErrors();
   g1->SetPoint(0,-4,-3);
   g1->SetPoint(1,1,1);
   g1->SetPoint(2,2,1);
   g1->SetPoint(3,3,4);
   g1->SetPoint(4,5,5);
   g1->SetPointError(0,1.,2.);
   g1->SetPointError(1,2,1);
   g1->SetPointError(2,2,3);
   g1->SetPointError(3,3,2);
   g1->SetPointError(4,4,5);
   g1->SetMarkerStyle(21);
 
   auto *g2 = new TGraph();
   g2->SetPoint(0,4,8);
   g2->SetPoint(1,5,9);
   g2->SetPoint(2,6,10);
   g2->SetPoint(3,10,11);
   g2->SetPoint(4,15,12);
   g2->SetLineColor(kRed);
   g2->SetLineWidth(5);
 
   auto mg = new TMultiGraph();
   mg->Add(g1,"P");
   mg->Add(g2,"L");
 
   c->cd(1); gPad->SetGrid(1,1);
   mg->Draw("A");
 
   c->cd(2); gPad->SetGrid(1,1);
   mg->Draw("A RX RY");
}

MultiGraphs' fitting

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");
}

Fit box position

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");
 
   if (stats1 && stats2) {
      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();
   }
}

Axis' limits setting

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.);
}

Definition at line 34 of file TMultiGraph.h.

Public Member Functions
	TMultiGraph ()
	TMultiGraph default constructor.
	TMultiGraph (const char *name, const char *title)
	Constructor with name and title.
	~TMultiGraph () override
	TMultiGraph destructor.
virtual void	Add (TGraph *graph, Option_t *chopt="")
	Add a new graph to the list of graphs.
virtual void	Add (TMultiGraph *multigraph, Option_t *chopt="")
	Add all the graphs in "multigraph" to the list of graphs.
TIter	begin () const
	Get iterator over internal graphs list.
void	Browse (TBrowser *b) override
	Browse multigraph.
Int_t	DistancetoPrimitive (Int_t px, Int_t py) override
	Compute distance from point px,py to each graph.
void	Draw (Option_t *chopt="") override
	Draw this multigraph with its current attributes.
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.
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.
virtual void	FitPanel ()
	Display a panel with all histogram fit options.
TF1 *	GetFunction (const char *name) const
	Return pointer to function with name.
virtual Option_t *	GetGraphDrawOption (const TGraph *gr) const
	Return the draw option for the TGraph gr in this TMultiGraph.
TH1F *	GetHistogram ()
	Returns a pointer to the histogram used to draw the axis.
TList *	GetListOfFunctions ()
	Return pointer to list of functions.
const TList *	GetListOfFunctions () const
TList *	GetListOfGraphs () const
TAxis *	GetXaxis ()
	Get x axis of the graph.
TAxis *	GetYaxis ()
	Get y axis of the graph.
virtual void	InitExpo (Double_t xmin, Double_t xmax)
	Compute Initial values of parameters for an exponential.
virtual void	InitGaus (Double_t xmin, Double_t xmax)
	Compute Initial values of parameters for a gaussian.
virtual void	InitPolynom (Double_t xmin, Double_t xmax)
	Compute Initial values of parameters for a polynom.
TClass *	IsA () const override
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.
virtual void	LeastSquareFit (Int_t m, Double_t *a, Double_t xmin, Double_t xmax)
	Least squares lpolynomial fitting without weights.
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.
void	Paint (Option_t *chopt="") override
	Paint all the graphs of this multigraph.
void	PaintPads (Option_t *chopt="")
	Divides the active pad and draws all Graphs in the Multigraph separately.
void	PaintPolyLine3D (Option_t *chopt="")
	Paint all the graphs of this multigraph as 3D lines.
void	PaintReverse (Option_t *chopt="")
	Paint all the graphs of this multigraph reverting values along X and/or Y axis.
void	Print (Option_t *chopt="") const override
	Print the list of graphs.
void	RecursiveRemove (TObject *obj) override
	Recursively remove this object from a list.
void	SavePrimitive (std::ostream &out, Option_t *option="") override
	Save primitive as a C++ statement(s) on output stream out.
virtual void	SetMaximum (Double_t maximum=-1111)
	Set multigraph maximum.
virtual void	SetMinimum (Double_t minimum=-1111)
	Set multigraph minimum.
void	Streamer (TBuffer &) override
	Stream an object of class TObject.
void	StreamerNVirtual (TBuffer &ClassDef_StreamerNVirtual_b)
Public Member Functions inherited from TNamed
	TNamed ()
	TNamed (const char *name, const char *title)
	TNamed (const TNamed &named)
	TNamed copy ctor.
	TNamed (const TString &name, const TString &title)
virtual	~TNamed ()
	TNamed destructor.
void	Clear (Option_t *option="") override
	Set name and title to empty strings ("").
TObject *	Clone (const char *newname="") const override
	Make a clone of an object using the Streamer facility.
Int_t	Compare (const TObject *obj) const override
	Compare two TNamed objects.
void	Copy (TObject &named) const override
	Copy this to obj.
virtual void	FillBuffer (char *&buffer)
	Encode TNamed into output buffer.
const char *	GetName () const override
	Returns name of object.
const char *	GetTitle () const override
	Returns title of object.
ULong_t	Hash () const override
	Return hash value for this object.
TClass *	IsA () const override
Bool_t	IsSortable () const override
void	ls (Option_t *option="") const override
	List TNamed name and title.
TNamed &	operator= (const TNamed &rhs)
	TNamed assignment operator.
void	Print (Option_t *option="") const override
	Print TNamed name and title.
virtual void	SetName (const char *name)
	Set the name of the TNamed.
virtual void	SetNameTitle (const char *name, const char *title)
	Set all the TNamed parameters (name and title).
virtual void	SetTitle (const char *title="")
	Set the title of the TNamed.
virtual Int_t	Sizeof () const
	Return size of the TNamed part of the TObject.
void	Streamer (TBuffer &) override
	Stream an object of class TObject.
void	StreamerNVirtual (TBuffer &ClassDef_StreamerNVirtual_b)
Public Member Functions inherited from TObject
	TObject ()
	TObject constructor.
	TObject (const TObject &object)
	TObject copy ctor.
virtual	~TObject ()
	TObject destructor.
void	AbstractMethod (const char *method) const
	Use this method to implement an "abstract" method that you don't want to leave purely abstract.
virtual void	AppendPad (Option_t *option="")
	Append graphics object to current pad.
ULong_t	CheckedHash ()
	Check and record whether this class has a consistent Hash/RecursiveRemove setup (*) and then return the regular Hash value for this object.
virtual const char *	ClassName () const
	Returns name of class to which the object belongs.
virtual void	Delete (Option_t *option="")
	Delete this object.
virtual void	DrawClass () const
	Draw class inheritance tree of the class to which this object belongs.
virtual TObject *	DrawClone (Option_t *option="") const
	Draw a clone of this object in the current selected pad with: gROOT->SetSelectedPad(c1).
virtual void	Dump () const
	Dump contents of object on stdout.
virtual void	Error (const char *method, const char *msgfmt,...) const
	Issue error message.
virtual void	Execute (const char *method, const char *params, Int_t *error=nullptr)
	Execute method on this object with the given parameter string, e.g.
virtual void	Execute (TMethod *method, TObjArray *params, Int_t *error=nullptr)
	Execute method on this object with parameters stored in the TObjArray.
virtual void	ExecuteEvent (Int_t event, Int_t px, Int_t py)
	Execute action corresponding to an event at (px,py).
virtual void	Fatal (const char *method, const char *msgfmt,...) const
	Issue fatal error message.
virtual TObject *	FindObject (const char *name) const
	Must be redefined in derived classes.
virtual TObject *	FindObject (const TObject *obj) const
	Must be redefined in derived classes.
virtual Option_t *	GetDrawOption () const
	Get option used by the graphics system to draw this object.
virtual const char *	GetIconName () const
	Returns mime type name of object.
virtual char *	GetObjectInfo (Int_t px, Int_t py) const
	Returns string containing info about the object at position (px,py).
virtual Option_t *	GetOption () const
virtual UInt_t	GetUniqueID () const
	Return the unique object id.
virtual Bool_t	HandleTimer (TTimer *timer)
	Execute action in response of a timer timing out.
Bool_t	HasInconsistentHash () const
	Return true is the type of this object is known to have an inconsistent setup for Hash and RecursiveRemove (i.e.
virtual void	Info (const char *method, const char *msgfmt,...) const
	Issue info message.
virtual Bool_t	InheritsFrom (const char *classname) const
	Returns kTRUE if object inherits from class "classname".
virtual Bool_t	InheritsFrom (const TClass *cl) const
	Returns kTRUE if object inherits from TClass cl.
virtual void	Inspect () const
	Dump contents of this object in a graphics canvas.
void	InvertBit (UInt_t f)
Bool_t	IsDestructed () const
	IsDestructed.
virtual Bool_t	IsEqual (const TObject *obj) const
	Default equal comparison (objects are equal if they have the same address in memory).
virtual Bool_t	IsFolder () const
	Returns kTRUE in case object contains browsable objects (like containers or lists of other objects).
R__ALWAYS_INLINE Bool_t	IsOnHeap () const
R__ALWAYS_INLINE Bool_t	IsZombie () const
void	MayNotUse (const char *method) const
	Use this method to signal that a method (defined in a base class) may not be called in a derived class (in principle against good design since a child class should not provide less functionality than its parent, however, sometimes it is necessary).
virtual Bool_t	Notify ()
	This method must be overridden to handle object notification (the base implementation is no-op).
void	Obsolete (const char *method, const char *asOfVers, const char *removedFromVers) const
	Use this method to declare a method obsolete.
void	operator delete (void *ptr)
	Operator delete.
void	operator delete (void *ptr, void *vp)
	Only called by placement new when throwing an exception.
void	operator delete[] (void *ptr)
	Operator delete [].
void	operator delete[] (void *ptr, void *vp)
	Only called by placement new[] when throwing an exception.
void *	operator new (size_t sz)
void *	operator new (size_t sz, void *vp)
void *	operator new[] (size_t sz)
void *	operator new[] (size_t sz, void *vp)
TObject &	operator= (const TObject &rhs)
	TObject assignment operator.
virtual void	Pop ()
	Pop on object drawn in a pad to the top of the display list.
virtual Int_t	Read (const char *name)
	Read contents of object with specified name from the current directory.
void	ResetBit (UInt_t f)
virtual void	SaveAs (const char *filename="", Option_t *option="") const
	Save this object in the file specified by filename.
void	SetBit (UInt_t f)
void	SetBit (UInt_t f, Bool_t set)
	Set or unset the user status bits as specified in f.
virtual void	SetDrawOption (Option_t *option="")
	Set drawing option for object.
virtual void	SetUniqueID (UInt_t uid)
	Set the unique object id.
void	StreamerNVirtual (TBuffer &ClassDef_StreamerNVirtual_b)
virtual void	SysError (const char *method, const char *msgfmt,...) const
	Issue system error message.
R__ALWAYS_INLINE Bool_t	TestBit (UInt_t f) const
Int_t	TestBits (UInt_t f) const
virtual void	UseCurrentStyle ()
	Set current style settings in this object This function is called when either TCanvas::UseCurrentStyle or TROOT::ForceStyle have been invoked.
virtual void	Warning (const char *method, const char *msgfmt,...) const
	Issue warning message.
virtual Int_t	Write (const char *name=nullptr, Int_t option=0, Int_t bufsize=0)
	Write this object to the current directory.
virtual Int_t	Write (const char *name=nullptr, Int_t option=0, Int_t bufsize=0) const
	Write this object to the current directory.

Static Public Member Functions
static TClass *	Class ()
static const char *	Class_Name ()
static constexpr Version_t	Class_Version ()
static const char *	DeclFileName ()
Static Public Member Functions inherited from TNamed
static TClass *	Class ()
static const char *	Class_Name ()
static constexpr Version_t	Class_Version ()
static const char *	DeclFileName ()
Static Public Member Functions inherited from TObject
static TClass *	Class ()
static const char *	Class_Name ()
static constexpr Version_t	Class_Version ()
static const char *	DeclFileName ()
static Longptr_t	GetDtorOnly ()
	Return destructor only flag.
static Bool_t	GetObjectStat ()
	Get status of object stat flag.
static void	SetDtorOnly (void *obj)
	Set destructor only flag.
static void	SetObjectStat (Bool_t stat)
	Turn on/off tracking of objects in the TObjectTable.

Protected Member Functions
	TMultiGraph (const TMultiGraph &)=delete
TMultiGraph &	operator= (const TMultiGraph &)=delete
Protected Member Functions inherited from TObject
virtual void	DoError (int level, const char *location, const char *fmt, va_list va) const
	Interface to ErrorHandler (protected).
void	MakeZombie ()

Protected Attributes
TList *	fFunctions {nullptr}
	Pointer to list of functions (fits and user)
TList *	fGraphs {nullptr}
	Pointer to list of TGraphs.
TH1F *	fHistogram {nullptr}
	Pointer to histogram used for drawing axis.
Double_t	fMaximum {-1111}
	Maximum value for plotting along y.
Double_t	fMinimum {-1111}
	Minimum value for plotting along y.
Protected Attributes inherited from TNamed
TString	fName
TString	fTitle

Additional Inherited Members
Public Types inherited from TObject
enum	{   kIsOnHeap = 0x01000000 , kNotDeleted = 0x02000000 , kZombie = 0x04000000 , kInconsistent = 0x08000000 ,   kBitMask = 0x00ffffff }
enum	{ kSingleKey = (1ULL << ( 0 )) , kOverwrite = (1ULL << ( 1 )) , kWriteDelete = (1ULL << ( 2 )) }
enum	EDeprecatedStatusBits { kObjInCanvas = (1ULL << ( 3 )) }
enum	EStatusBits {   kCanDelete = (1ULL << ( 0 )) , kMustCleanup = (1ULL << ( 3 )) , kIsReferenced = (1ULL << ( 4 )) , kHasUUID = (1ULL << ( 5 )) ,   kCannotPick = (1ULL << ( 6 )) , kNoContextMenu = (1ULL << ( 8 )) , kInvalidObject = (1ULL << ( 13 )) }
Protected Types inherited from TObject
enum	{ kOnlyPrepStep = (1ULL << ( 3 )) }

#include <TMultiGraph.h>

Inheritance diagram for TMultiGraph:

Constructor & Destructor Documentation

TMultiGraph() [1/3]

TMultiGraph::TMultiGraph ( const TMultiGraph &  )

protecteddelete

TMultiGraph() [2/3]

TMultiGraph::TMultiGraph

(

)

TMultiGraph default constructor.

Definition at line 369 of file TMultiGraph.cxx.

TMultiGraph() [3/3]

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

Constructor with name and title.

Definition at line 377 of file TMultiGraph.cxx.

~TMultiGraph()

TMultiGraph::~TMultiGraph ( )

override

TMultiGraph destructor.

Definition at line 385 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 421 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 437 of file TMultiGraph.cxx.

begin()

TIter TMultiGraph::begin

(

)

const

Get iterator over internal graphs list.

Definition at line 1654 of file TMultiGraph.cxx.

Browse()

void TMultiGraph::Browse ( TBrowser *  b )

overridevirtual

Browse multigraph.

Reimplemented from TObject.

Definition at line 458 of file TMultiGraph.cxx.

Class()

static TClass * TMultiGraph::Class ( )

static

Returns

TClass describing this class

Class_Name()

static const char * TMultiGraph::Class_Name ( )

static

Returns

Name of this class

Class_Version()

static constexpr Version_t TMultiGraph::Class_Version ( )

inlinestaticconstexpr

Returns

Version of this class

Definition at line 85 of file TMultiGraph.h.

DeclFileName()

static const char * TMultiGraph::DeclFileName ( )

inlinestatic

Returns

Name of the file containing the class declaration

Definition at line 85 of file TMultiGraph.h.

DistancetoPrimitive()

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

overridevirtual

Compute distance from point px,py to each graph.

Reimplemented from TObject.

Definition at line 473 of file TMultiGraph.cxx.

Draw()

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

overridevirtual

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 510 of file TMultiGraph.cxx.

end()

TIter TMultiGraph::end ( ) const

inline

Definition at line 70 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 528 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" Ignore all the point errors
• "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 701 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 718 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 1088 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 742 of file TMultiGraph.cxx.

GetHistogram()

TH1F * TMultiGraph::GetHistogram

(

)

Returns a pointer to the histogram used to draw the axis.

Takes into account following cases.

1. if fHistogram exists it is returned
2. if fHistogram doesn't exists and gPad exists gPad is updated. That may trigger the creation of fHistogram. If fHistogram still does not exit but hframe does (if user called TPad::DrawFrame) the pointer to hframe histogram is returned
3. after the two previous steps, if fHistogram still doesn't exist, then it is created.

Definition at line 1017 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 1098 of file TMultiGraph.cxx.

GetListOfFunctions() [2/2]

const TList * TMultiGraph::GetListOfFunctions ( ) const

inline

Definition at line 72 of file TMultiGraph.h.

GetListOfGraphs()

TList * TMultiGraph::GetListOfGraphs ( ) const

inline

Definition at line 68 of file TMultiGraph.h.

GetXaxis()

TAxis * TMultiGraph::GetXaxis

(

)

Get x axis of the graph.

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

Definition at line 1109 of file TMultiGraph.cxx.

GetYaxis()

TAxis * TMultiGraph::GetYaxis

(

)

Get y axis of the graph.

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

Definition at line 1121 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 802 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 757 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 819 of file TMultiGraph.cxx.

IsA()

TClass * TMultiGraph::IsA ( ) const

inlineoverridevirtual

Returns

TClass describing current object

Reimplemented from TObject.

Definition at line 85 of file TMultiGraph.h.

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 991 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 843 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 938 of file TMultiGraph.cxx.

operator=()

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

protecteddelete

Paint()

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

overridevirtual

Paint all the graphs of this multigraph.

Reimplemented from TObject.

Definition at line 1132 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 1379 of file TMultiGraph.cxx.

PaintPolyLine3D()

void TMultiGraph::PaintPolyLine3D

(

Option_t *

chopt = ""

)

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

Definition at line 1419 of file TMultiGraph.cxx.

PaintReverse()

void TMultiGraph::PaintReverse

(

Option_t *

option = ""

)

Paint all the graphs of this multigraph reverting values along X and/or Y axis.

New graphs are created.

Definition at line 1520 of file TMultiGraph.cxx.

Print()

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

overridevirtual

Print the list of graphs.

Reimplemented from TObject.

Definition at line 1555 of file TMultiGraph.cxx.

RecursiveRemove()

void TMultiGraph::RecursiveRemove ( TObject *  obj )

overridevirtual

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 1571 of file TMultiGraph.cxx.

SavePrimitive()

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

overridevirtual

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

Reimplemented from TObject.

Definition at line 1595 of file TMultiGraph.cxx.

SetMaximum()

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

virtual

Set multigraph maximum.

Definition at line 1634 of file TMultiGraph.cxx.

SetMinimum()

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

virtual

Set multigraph minimum.

Definition at line 1644 of file TMultiGraph.cxx.

Streamer()

void TMultiGraph::Streamer ( TBuffer &  R__b )

overridevirtual

Stream an object of class TObject.

Reimplemented from TObject.

StreamerNVirtual()

void TMultiGraph::StreamerNVirtual ( TBuffer &  ClassDef_StreamerNVirtual_b )

inline

Definition at line 85 of file TMultiGraph.h.

Member Data Documentation

fFunctions

TList* TMultiGraph::fFunctions {nullptr}

protected

Pointer to list of functions (fits and user)

Definition at line 38 of file TMultiGraph.h.

fGraphs

TList* TMultiGraph::fGraphs {nullptr}

protected

Pointer to list of TGraphs.

Definition at line 37 of file TMultiGraph.h.

fHistogram

TH1F* TMultiGraph::fHistogram {nullptr}

protected

Pointer to histogram used for drawing axis.

Definition at line 39 of file TMultiGraph.h.

fMaximum

Double_t TMultiGraph::fMaximum {-1111}

protected

Maximum value for plotting along y.

Definition at line 40 of file TMultiGraph.h.

fMinimum

Double_t TMultiGraph::fMinimum {-1111}

protected

Minimum value for plotting along y.

Definition at line 41 of file TMultiGraph.h.

Libraries for TMultiGraph:

---

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

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