Normalizing a Histogram

Image produced by `.x NormalizeHistogram.C`

Two different methods of normalizing histograms
are shown, each with the original histogram.
next to the normalized one.

**Author:** Advait Dhingra

*This notebook tutorial was automatically generated with ROOTBOOK-izer from the macro found in the ROOT repository on Thursday, May 19, 2022 at 08:14 AM.*

In [1]:

```
%%cpp -d
#include "TH2F.h"
#include "TRandom.h"
#include "TCanvas.h"
```

In [2]:

```
std::array<double, 6> binsx{0, 5, 10, 20, 50, 100};
TH1F *orig = new TH1F("orig", "Original histogram before normalization", binsx.size() - 1, &binsx[0]);
gStyle->SetTitleFontSize(0.06);
TRandom2 rand;
```

Filling histogram with random entries

In [3]:

```
for (int i = 0; i < 100'000; ++i) {
double r = rand.Rndm() * 100;
orig->Fill(r);
}
TH1F *norm = (TH1F *)orig->Clone("norm");
norm->SetTitle("Normalized Histogram");
```

Normalizing the histogram by scaling by 1 / the integral and taking width into account

In [4]:

```
norm->Scale(1. / norm->Integral(), "width");
```

Drawing everything

In [5]:

```
TCanvas *c1 = new TCanvas("c1", "Histogram Normalization", 700, 900);
c1->Divide(1, 2);
c1->cd(1);
orig->Draw();
c1->cd(2);
norm->Draw();
```

Draw all canvases

In [6]:

```
%jsroot on
gROOT->GetListOfCanvases()->Draw()
```