Manipulating Histogram Data and Fill in a New Histogram

Newbie
1

I have a histogram in a ROOT file whose x-axis is channel number and y-axis is number of hits. I am trying to divide number of hits by total entries of a histogram and plot this hitrate in new histogram where x-axis is channel number and y-axis in hitrate.

11 void code() {
 12         TFile *file = new TFile("onmon_r1169_s1-92.root", "READ");
 13         TH1F *hist = (TH1F*)file->Get("SSDProfile_14");
 14         int entries = hist->GetEntries();
 15 //      cout << entries << endl; //Output: 503071
 16 
 17         TH1F* new_hist = new TH1F("hitrate", "hitrate per channel", 100, 0, 700);
 18 
 19         for (int i = 0; i <= entries; i++) {
 20                 //hist->GetBinContent(i);
 21                 double bin_content = hist->GetBinContent(i); 
 22                 double hitrate = bin_content/entries;
 23                 new_hist->SetBinContent(i, hitrate);
 24         }       
 25 
 26         new_hist->Draw();
 27 
 28 }

However, the histogram I produced is not as expected. I think I am messing up on GetBinContent part. Please let me know how I can fix the issue. Thank you.

2

You should do loop over the numver of bins hist->GetNbinsX().

...
for (int i = 1; i <= hist->GetNbinsX(); i++) {
...
3 
TH1F *new_hist = (TH1F*)hist->Clone("hitrate");
new_hist->SetTitle("hitrate per channel;channel;hitrate");
new_hist->Scale(1. / new_hist->Integral());
new_hist->Draw("HIST");