This example demonstrates how to display a histogram and its two projections. A TExec allows to redraw automatically the projections when a zoom is performed on the 2D histogram.
Author: Olivier Couet
This notebook tutorial was automatically generated with ROOTBOOK-izer from the macro found in the ROOT repository on Monday, September 16, 2024 at 02:41 PM.
TH2F *h2;
TH1D * projh2X;
TH1D * projh2Y;
TPad *right_pad, *top_pad;
Definition of a helper function:
%%cpp -d
void ZoomExec()
{
int xfirst = h2->GetXaxis()->GetFirst();
int xlast = h2->GetXaxis()->GetLast();
double xmin = h2->GetXaxis()->GetBinLowEdge(xfirst);
double xmax = h2->GetXaxis()->GetBinUpEdge(xlast);
projh2X->GetXaxis()->SetRangeUser(xmin, xmax);
top_pad->Modified();
int yfirst = h2->GetYaxis()->GetFirst();
int ylast = h2->GetYaxis()->GetLast();
double ymin = h2->GetYaxis()->GetBinLowEdge(yfirst);
double ymax = h2->GetYaxis()->GetBinUpEdge(ylast);
projh2Y->GetXaxis()->SetRangeUser(ymin, ymax);
right_pad->Modified();
}
auto c1 = new TCanvas("c1", "c1",900,900);
gStyle->SetOptStat(0);
TPad *center_pad = new TPad("center_pad", "center_pad",0.0,0.0,0.6,0.6);
center_pad->Draw();
right_pad = new TPad("right_pad", "right_pad",0.55,0.0,1.0,0.6);
right_pad->Draw();
top_pad = new TPad("top_pad", "top_pad",0.0,0.55,0.6,1.0);
top_pad->Draw();
h2 = new TH2F("h2","",40,-4,4,40,-20,20);
Float_t px, py;
for (Int_t i = 0; i < 25000; i++) {
gRandom->Rannor(px,py);
h2->Fill(px,5*py);
}
projh2X = h2->ProjectionX();
projh2Y = h2->ProjectionY();
center_pad->cd();
gStyle->SetPalette(1);
h2->Draw("COL");
top_pad->cd();
projh2X->SetFillColor(kBlue+1);
projh2X->Draw("bar");
right_pad->cd();
projh2Y->SetFillColor(kBlue-2);
projh2Y->Draw("hbar");
c1->cd();
TLatex t;
t.SetTextFont(42);
t.SetTextSize(0.02);
t.DrawLatex(0.6,0.88,"This example demonstrates how to display");
t.DrawLatex(0.6,0.85,"a histogram and its two projections.");
auto ex = new TExec("zoom","ZoomExec()");
h2->GetListOfFunctions()->Add(ex);
Draw all canvases
%jsroot on
gROOT->GetListOfCanvases()->Draw()