Integral of a specific region on the x and y-axis in histogram

[Munirat]

Pls in getting a count under a particular peak I usually use something like this
energy->Integral(20,50)
and it gives me the integral in that region of the x-axis.
But my peak does not start from zero on the y-axis want to know if there is a way to get an integral starting for instance from 100 on the y-axis and 20-50 on the x-axis.
Thanks

[Wile_E_Coyote]

TH2::Integral

[Munirat]

How should I write it pls

[ksmith]

The documentation provided is pretty clear:

@https://root.cern.ch/doc/master/classTH2.html#ae6947333287c56b92e83e5f1983b8701

Double_t TH2::Integral 	( 	Int_t  	firstxbin,
		Int_t  	lastxbin,
		Int_t  	firstybin,
		Int_t  	lastybin,
		Option_t *  	option = "" 
	) 		const
	virtual

Return integral of bin contents in range [firstxbin,lastxbin],[firstybin,lastybin] for a 2-D histogram By default the integral is computed as the sum of bin contents in the range.

if option “width” is specified, the integral is the sum of the bin contents multiplied by the bin width in x and in y.

Definition at line 1201 of file TH2.cxx.

An example:

{                                                                                  
   TH2D *h = new TH2D("h","",200,0,250,200,-150,150);                                                                                                   
   for (int i=0;i<5000;i++) {                                                      
      double x = gRandom->Uniform(0,250);                                          
      double y = gRandom->Uniform(-150,150);                                       
      h->Fill(x,y);                                                                
   }                                                                               
                                                                                   
   //Integrate from bin (10,10) to bin (30,30)                                     
   std::cout << h->Integral(10, 30, 10, 30) << "\n";                               
                                                                                   
   //Integrate roughly from the point (10,10) to the point (30,30)                 
   int firstxbin = h->GetXaxis()->FindBin(10);                                     
   int lastxbin = h->GetXaxis()->FindBin(30);                                      
   int firstybin = h->GetYaxis()->FindBin(10);                                     
   int lastybin = h->GetYaxis()->FindBin(30);                                      
   std::cout << h->Integral(firstxbin, lastxbin, firstybin, lastybin) << "\n";     
}