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Reference Guide
canvas2.C File Reference

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Example of canvas partitioning.

Sometimes the Divide() method is not appropriate to divide a Canvas. Because of the left and right margins, all the pads do not have the same width and height. CanvasPartition does that properly. This example also ensure that the axis labels and titles have the same sizes and that the tick marks length is uniform. In addition, XtoPad and YtoPad allow to place graphics objects like text in the right place in each sub-pads.

void CanvasPartition(TCanvas *C,const Int_t Nx = 2,const Int_t Ny = 2,
Float_t lMargin = 0.15, Float_t rMargin = 0.05,
Float_t bMargin = 0.15, Float_t tMargin = 0.05);
double XtoPad(double x);
double YtoPad(double x);
void canvas2()
auto C = (TCanvas*) gROOT->FindObject("C");
if (C) delete C;
C = new TCanvas("C","canvas",1024,640);
// Number of PADS
const Int_t Nx = 5;
const Int_t Ny = 5;
// Margins
Float_t lMargin = 0.12;
Float_t rMargin = 0.05;
Float_t bMargin = 0.15;
Float_t tMargin = 0.05;
// Canvas setup
// Dummy histogram.
auto h = (TH1F*) gROOT->FindObject("histo");
if (h) delete h;
h = new TH1F("histo","",100,-5.0,5.0);
h->GetXaxis()->SetTitle("x axis");
h->GetYaxis()->SetTitle("y axis");
TPad *pad[Nx][Ny];
for (Int_t i = 0; i < Nx; i++) {
for (Int_t j = 0; j < Ny; j++) {
// Get the pads previously created.
pad[i][j] = (TPad*) C->FindObject(TString::Format("pad_%d_%d",i,j).Data());
// Size factors
Float_t xFactor = pad[0][0]->GetAbsWNDC()/pad[i][j]->GetAbsWNDC();
Float_t yFactor = pad[0][0]->GetAbsHNDC()/pad[i][j]->GetAbsHNDC();
TH1F *hFrame = (TH1F*) h->Clone(TString::Format("h_%d_%d",i,j).Data());
// y axis range
hFrame->SetMinimum(0.0001); // do not show 0
// Format for y axis
// TICKS Y Axis
// Format for x axis
// TICKS X Axis
// Draw cloned histogram with individual settings
text.DrawTextNDC(XtoPad(0.9), YtoPad(0.8), gPad->GetName());
void CanvasPartition(TCanvas *C,const Int_t Nx,const Int_t Ny,
Float_t lMargin, Float_t rMargin,
Float_t bMargin, Float_t tMargin)
if (!C) return;
// Setup Pad layout:
Float_t vSpacing = 0.0;
Float_t vStep = (1.- bMargin - tMargin - (Ny-1) * vSpacing) / Ny;
Float_t hSpacing = 0.0;
Float_t hStep = (1.- lMargin - rMargin - (Nx-1) * hSpacing) / Nx;
Float_t vposd,vposu,vmard,vmaru,vfactor;
Float_t hposl,hposr,hmarl,hmarr,hfactor;
for (Int_t i=0;i<Nx;i++) {
if (i==0) {
hposl = 0.0;
hposr = lMargin + hStep;
hfactor = hposr-hposl;
hmarl = lMargin / hfactor;
hmarr = 0.0;
} else if (i == Nx-1) {
hposl = hposr + hSpacing;
hposr = hposl + hStep + rMargin;
hfactor = hposr-hposl;
hmarl = 0.0;
hmarr = rMargin / (hposr-hposl);
} else {
hposl = hposr + hSpacing;
hposr = hposl + hStep;
hfactor = hposr-hposl;
hmarl = 0.0;
hmarr = 0.0;
for (Int_t j=0;j<Ny;j++) {
if (j==0) {
vposd = 0.0;
vposu = bMargin + vStep;
vfactor = vposu-vposd;
vmard = bMargin / vfactor;
vmaru = 0.0;
} else if (j == Ny-1) {
vposd = vposu + vSpacing;
vposu = vposd + vStep + tMargin;
vfactor = vposu-vposd;
vmard = 0.0;
vmaru = tMargin / (vposu-vposd);
} else {
vposd = vposu + vSpacing;
vposu = vposd + vStep;
vfactor = vposu-vposd;
vmard = 0.0;
vmaru = 0.0;
auto name = TString::Format("pad_%d_%d",i,j);
auto pad = (TPad*) C->FindObject(name.Data());
if (pad) delete pad;
pad = new TPad(name.Data(),"",hposl,vposd,hposr,vposu);
double XtoPad(double x)
double xl,yl,xu,yu;
double pw = xu-xl;
double lm = gPad->GetLeftMargin();
double rm = gPad->GetRightMargin();
double fw = pw-pw*lm-pw*rm;
return (x*fw+pw*lm)/pw;
double YtoPad(double y)
double xl,yl,xu,yu;
double ph = yu-yl;
double tm = gPad->GetTopMargin();
double bm = gPad->GetBottomMargin();
double fh = ph-ph*bm-ph*tm;
return (y*fh+bm*ph)/ph;
#define h(i)
Definition: RSha256.hxx:106
int Int_t
Definition: RtypesCore.h:45
float Float_t
Definition: RtypesCore.h:57
Option_t Option_t TPoint TPoint const char text
char name[80]
Definition: TGX11.cxx:110
#define gROOT
Definition: TROOT.h:404
R__EXTERN TStyle * gStyle
Definition: TStyle.h:414
#define gPad
Definition: TVirtualPad.h:288
virtual void SetTitleOffset(Float_t offset=1)
Set distance between the axis and the axis title.
Definition: TAttAxis.cxx:301
virtual void SetLabelSize(Float_t size=0.04)
Set size of axis labels.
Definition: TAttAxis.cxx:206
virtual void SetTitleFont(Style_t font=62)
Set the title font.
Definition: TAttAxis.cxx:330
virtual void SetLabelOffset(Float_t offset=0.005)
Set distance between the axis and the labels.
Definition: TAttAxis.cxx:194
virtual void SetLabelFont(Style_t font=62)
Set labels' font.
Definition: TAttAxis.cxx:183
virtual void SetTitleSize(Float_t size=0.04)
Set size of axis title.
Definition: TAttAxis.cxx:312
virtual void SetTickLength(Float_t length=0.03)
Set tick mark length.
Definition: TAttAxis.cxx:287
virtual void SetNdivisions(Int_t n=510, Bool_t optim=kTRUE)
Set the number of divisions for this axis.
Definition: TAttAxis.cxx:236
virtual void SetBottomMargin(Float_t bottommargin)
Set Pad bottom margin in fraction of the pad height.
Definition: TAttPad.cxx:99
virtual void SetLeftMargin(Float_t leftmargin)
Set Pad left margin in fraction of the pad width.
Definition: TAttPad.cxx:109
void SetFrameBorderMode(Int_t mode=1)
Definition: TAttPad.h:79
void SetFrameFillStyle(Style_t styl=0)
Definition: TAttPad.h:75
virtual void SetRightMargin(Float_t rightmargin)
Set Pad right margin in fraction of the pad width.
Definition: TAttPad.cxx:119
virtual void SetTopMargin(Float_t topmargin)
Set Pad top margin in fraction of the pad height.
Definition: TAttPad.cxx:129
void CenterTitle(Bool_t center=kTRUE)
Center axis title.
Definition: TAxis.h:185
The Canvas class.
Definition: TCanvas.h:23
1-D histogram with a float per channel (see TH1 documentation)}
Definition: TH1.h:577
TAxis * GetXaxis()
Definition: TH1.h:322
virtual void SetMaximum(Double_t maximum=-1111)
Definition: TH1.h:400
TAxis * GetYaxis()
Definition: TH1.h:323
void Draw(Option_t *option="") override
Draw this histogram with options.
Definition: TH1.cxx:3060
virtual void SetMinimum(Double_t minimum=-1111)
Definition: TH1.h:401
The most important graphics class in the ROOT system.
Definition: TPad.h:28
void SetBorderSize(Short_t bordersize) override
Definition: TPad.h:321
void SetFillStyle(Style_t fstyle) override
Override TAttFill::FillStyle for TPad because we want to handle style=0 as style 4000.
Definition: TPad.cxx:5897
Double_t GetAbsWNDC() const override
Definition: TPad.h:220
TVirtualPad * cd(Int_t subpadnumber=0) override
Set Current pad.
Definition: TPad.cxx:598
void Draw(Option_t *option="") override
Draw Pad in Current pad (re-parent pad if necessary).
Definition: TPad.cxx:1268
void SetBorderMode(Short_t bordermode) override
Definition: TPad.h:320
Double_t GetAbsHNDC() const override
Definition: TPad.h:221
const char * Data() const
Definition: TString.h:369
static TString Format(const char *fmt,...)
Static method which formats a string using a printf style format descriptor and return a TString.
Definition: TString.cxx:2345
void SetOptStat(Int_t stat=1)
The type of information printed in the histogram statistics box can be selected via the parameter mod...
Definition: TStyle.cxx:1589
Base class for several text objects.
Definition: TText.h:22
Double_t y[n]
Definition: legend1.C:17
Double_t x[n]
Definition: legend1.C:17
static double C[]
Olivier Couet

Definition in file canvas2.C.