Subtracting Histograms: A Quick Guide

[lavster]

can anyone tell me how to subtract histograms?

ive got to histograms already defined (pointers) called h1 and h2. and i want to make a third histogram object that is one subtract the other.

so far I've got TH1F h3 = (*h2)-(*h1);
and then after defining a new canvas I've got

h3.Draw();

but its not doing anything :(

thanks!

 

[jtbell]

Which software are you using?

 

[lavster]

lol i forgot that bit - root/C++ :)

 

[jtbell]

OK, I'll move this again to the "programming" forum...

 

[diggy]

I think you can do it by making a copy or clone of the first, A, and then using A->Add(B, -1), where B is your second histogram.

Likewise for normalization stuff in your other question, just use something like A->Divide(A->GetEntries), if that normalization function doesn't work.