Re: Projection of a histograms.....again...

Hello all,

I have problem with the effective entries. I don't think to have changed nothing, but now it seems to not work and I have that the effective entries are bigger than I expect of a quantity like the number of bin in the x axis.

Melinda

#if !defined(__CINT__) || defined(__MAKECINT__)
#include <TH2F.h>
#include <TCanvas.h>
#include <TStyle.h>
#include <TFile.h>
#include <TRandom3.>
#endif

void prova1(Int_t seed)
{

 TH2F *histo = new TH2F("histo","histo",256,-.5,255.5,256,-0.5,255.5);  TRandom3 *random= new TRandom3(seed);
 histo->Sumw2();
 for(Int_t i=1;i<=256;i++)
   {

     for(Int_t j=1;j<=256;j++)
       {
     histo->Fill(i-1.5,j-1.5,random->Rndm());//in order to fill the first

       }

   }

 TCanvas *canvas =new TCanvas("canvas","canvas");  canvas->cd();
 histo->Draw("colz");
 canvas->Update();
 gStyle->SetPalette(1);
 TH1D *px = histo->ProjectionX();
 Int_t nbins = px->GetXaxis()->GetNbins();  for (Int_t bin=1;bin<=nbins;bin++) {
   double y = px->GetBinContent(bin);
   double e = px->GetBinError(bin);
   double effe = 0;
   if (e != 0) effe = y*y/e*e;
   px->SetBinContent(bin,effe);
   px->SetBinError(bin,0);
 }

 TCanvas *canvas2 =new TCanvas("canvas2","canvas2");  canvas2->cd();
 px->Draw();
 canvas2->Update();

}

On Mon, Mar 10, 2008 at 5:23 PM, Lorenzo Moneta <lorenzo.moneta_at_cern.ch> wrote:

> Hello Melinda,
>  we will plan to add this new functionality as an option for all the
> histogram projected functions, not as a new method.
> It is expected to have this implemented for the development release
> schedule for April. Anyway I will let you know when it will be in the SVN
> trunk,
>
>  Best Regards
>
>  Lorenzo
>
> On Mar 5, 2008, at 6:25 PM, Melinda Siciliano wrote:
>
> Hi Rene and Lorenzo,
>
> I tried as Rene suggested me and it works! Thanks a lot!!!!
>
> May I ask you if when you put the new function in ROOT , could you tell me
> then the name of the function in the way to substite it in my gui?
>
> Thanks,
>
> Melinda
>
> On Tue, Mar 4, 2008 at 5:24 PM, Rene Brun <Rene.Brun_at_cern.ch> wrote:
>
> > Hi Melinda,
> >
> > The projection of the effective entries is currently not implemented.
> > It is not too complex to obtain what you want if you have called Sumw2
> > on your TH2 object.
> > In this case, make the projection using TH2::ProjectionX (or Y) and
> > compute the effective entries
> > with a code looking like
> >     TH2 *h2;  //your Th2 object where Sumw2 has been called before
> > filling
> >     TH1D *px = h2->ProjectionX();
> >     Int_t nbins = px->GetXaxis()->GetNbins();
> >     for (Int_t bin=1;bin<=nbins;bin++) {
> >        double y = px->GetBinContent(bin);
> >        double e = px->GetBinError(bin);
> >        double effe = 0;
> >        if (e != 0) effe = y*y/e*e;
> >        px->SetBinContent(bin,effe);
> >       px->SetBinError(bin,0);
> >   }
> >
> > This could be an option when calling TH2::ProjectionX,Y.
> > Lorenzo, could you implement this code in all Projection functions?
> >
> > Rene Brun
> >
> > Melinda Siciliano wrote:
> > > Dear all,
> > >
> > > I have an 2D-histogram filled using the weight. I would like to ask
> > > you if there a way to make the projection of the effective entries of
> > > the histogram.
> > >
> > > Thanks,
> > >
> > > Melinda
> >
> >
>
>