root_plot

multi-picture layout

CanvasPartition is helpful for you to draw a multi-picture layout, instead of using canvas->Divide().

code 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.

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;
}

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Last update: 2025-04-14
Created: 2025-04-01