canvas2.C File Reference

Detailed Description

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()
{
   gStyle->SetOptStat(0);
 
   auto C = (TCanvas *)gROOT->FindObject("C");
   if (C)
      delete C;
   C = new TCanvas("C", "canvas", 1024, 640);
   C->SetFillStyle(4000);
 
   // 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
   CanvasPartition(C, Nx, Ny, lMargin, rMargin, bMargin, tMargin);
 
   // Dummy histogram.
   auto h = (TH1F *)gROOT->FindObject("histo");
   if (h)
      delete h;
   h = new TH1F("histo", "", 100, -5.0, 5.0);
   h->FillRandom("gaus", 10000);
   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++) {
         C->cd(0);
 
         // Get the pads previously created.
         pad[i][j] = (TPad *)C->FindObject(TString::Format("pad_%d_%d", i, j).Data());
         pad[i][j]->Draw();
         pad[i][j]->SetFillStyle(4000);
         pad[i][j]->SetFrameFillStyle(4000);
         pad[i][j]->cd();
 
         // 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
         hFrame->SetMaximum(1.2 * h->GetMaximum());
 
         // Format for y axis
         hFrame->GetYaxis()->SetLabelFont(43);
         hFrame->GetYaxis()->SetLabelSize(16);
         hFrame->GetYaxis()->SetLabelOffset(0.02);
         hFrame->GetYaxis()->SetTitleFont(43);
         hFrame->GetYaxis()->SetTitleSize(16);
         hFrame->GetYaxis()->SetTitleOffset(2);
 
         hFrame->GetYaxis()->CenterTitle();
         hFrame->GetYaxis()->SetNdivisions(505);
 
         // TICKS Y Axis
         hFrame->GetYaxis()->SetTickLength(xFactor * 0.04 / yFactor);
 
         // Format for x axis
         hFrame->GetXaxis()->SetLabelFont(43);
         hFrame->GetXaxis()->SetLabelSize(16);
         hFrame->GetXaxis()->SetLabelOffset(0.02);
         hFrame->GetXaxis()->SetTitleFont(43);
         hFrame->GetXaxis()->SetTitleSize(16);
         hFrame->GetXaxis()->SetTitleOffset(1);
         hFrame->GetXaxis()->CenterTitle();
         hFrame->GetXaxis()->SetNdivisions(505);
 
         // TICKS X Axis
         hFrame->GetXaxis()->SetTickLength(yFactor * 0.06 / xFactor);
 
         // Draw cloned histogram with individual settings
         hFrame->Draw();
 
         TText text;
         text.SetTextAlign(31);
         text.SetTextFont(43);
         text.SetTextSize(10);
         text.DrawTextNDC(XtoPad(0.9), YtoPad(0.8), gPad->GetName());
      }
   }
   C->cd();
}
 
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;
         }
 
         C->cd(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);
         pad->SetLeftMargin(hmarl);
         pad->SetRightMargin(hmarr);
         pad->SetBottomMargin(vmard);
         pad->SetTopMargin(vmaru);
 
         pad->SetFrameBorderMode(0);
         pad->SetBorderMode(0);
         pad->SetBorderSize(0);
 
         pad->Draw();
      }
   }
}
 
double XtoPad(double x)
{
   double xl, yl, xu, yu;
   gPad->GetPadPar(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;
   gPad->GetPadPar(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;
}

Author

Olivier Couet

Definition in file canvas2.C.