Zooming a region in a histogram plot

[ctorresc]

Iḿ trying to do something like this in a histogram in ROOT to visualize some error bars better. Any ideas?

I don’t really find any documentation or questions in the forum about this topic. Someone have a link to the documentation or have any ideas?

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ROOT Version: ROOT 6.22
Platform: Ubuntu 20.04.2 LTS/02

[dastudillo]

How to zoom a portion of a histogram and insert over the same histogram

Hi everyone! I am new to this forum. I want to zoom a portion of a histogram and to put it on the same histogram in order to see the low energy peaks. I don’t have any idea how to proceed. I am attaching the picture in which this job is done and i want to plot exactly the same way. Thank you [zoom]

[couet]

Double_t g2(Double_t *x, Double_t *par) {
   Double_t r1 = Double_t((x[0]-par[1])/par[2]);
   Double_t r2 = Double_t((x[1]-par[3])/par[4]);
   return par[0]*TMath::Exp(-0.5*(r1*r1+r2*r2));
}
Double_t fun2(Double_t *x, Double_t *par) {
   Double_t *p1 = &par[0];
   Double_t *p2 = &par[5];
   Double_t *p3 = &par[10];
   Double_t result = g2(x,p1) + g2(x,p2) + g2(x,p3);
   return result;
}

void zoomth2() {
   gStyle->SetOptStat(0);
   const Int_t npar = 15;
   Double_t f2params[npar] =
      {100,-3,3,-3,3,160,0,0.8,0,0.9,40,4,0.7,4,0.7};
   TF2 *f2 = new TF2("f2",fun2,-10,10,-10,10, npar);
   f2->SetParameters(f2params);

   //Create an histogram and fill it randomly with f2
   TH2F *h2 = new TH2F("h2","TH2 Zoom",100,-40,150,100,-40,150);
   Int_t nentries = 1000000;
   h2->FillRandom("f2",nentries);
   h2->Draw("col");

   TBox *b = new TBox(-20,-20,20,20);
   b->SetFillStyle(0);
   b->SetLineColor(1);
   b->Draw();

   TLine *l1 = new TLine (-20,20,58.74284,146.25);
   l1->Draw();
   TLine *l2 = new TLine (20,-20,140.4047,55.75);
   l2->Draw();

   TPad *p = new TPad("p","p", 0.5,0.5,0.9,0.9);
   p->SetLeftMargin(0);
   p->SetBottomMargin(0);
   p->Draw();
   p->cd();
   TH2D *h2z = (TH2D *)h2->DrawCopy("col");
   TAxis *xa = h2z->GetXaxis();
   TAxis *ya = h2z->GetYaxis();
   xa->SetRangeUser(-20.,20.);
   ya->SetRangeUser(-20.,20.);
   xa->SetLabelSize(0.);
   xa->SetTickSize(0.);
   ya->SetLabelSize(0.);
   ya->SetTickSize(0.);
}