Nick van Eijndhoven wrote:
>
> Dear friends,
> In ROOT I have 3 histos (1 dimensional), h1, h2 and h3.
> h1 I fit with some function f and now I would like to subtract
> h3 from h2 in which I weight each bin of h3 with the function value of
> f in that bin. I.e. result= h3 - f(x)*h2.
> Could anyone of you tell me the most effective (c.q. elegant) way to
> do this, such that I don't have to change all the code when changing the
> function f ?
Below is a script illustrating a possible solution:
Rene Brun
{
gROOT->Reset();
TFile f("hsimple.root"); //assume a file with histogram named hpx
Int_t ncx = hpx->GetNbinsX();
TH1F hnew = *hpx; //copy hpx to hnew
hnew.Reset();
TFormula f1("f1","x*x*x");
for (Int_t bin=1;bin<=ncx;bin++) { //fill hnew with function values
Float_t x = hnew.GetBinCenter(bin);
hnew.Fill(x, f1.Eval(x));
}
TH1F hresult = hnew*(*hpx); //make result histogram
//you could also do directly
TH1F hresult = h1 -hnew*(*hpx);
hresult.Draw();
}
This archive was generated by hypermail 2b29 : Tue Jan 04 2000 - 00:26:19 MET