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

Hi Melinda,

  the number of entry /bin will be 256 but this value is not stored by the ROOT histogram and is not equal to the bin content when you fill an histogram with weights. The number of effective entries/bin deduced from the bin content and bin errors will be then different than 256.

The result obtained looks fine to me,

  Ciao

  Lorenzo
On Mar 13, 2008, at 2:47 PM, Melinda Siciliano wrote:

> Hi,
>
> I expect 256 entries per bin of the projection because I filled each
> cell of the 2D histogram only once and with something that is
> different from 0. In fact, in the macro I sent today I don't fill
> the histogram if the random number I obtained is equal to 0. So,
> what I expect is that each cell of the 2D histogram will have only
> one entry with a weight different from 0 and If I will do a
> projection respect to one axis and the calculation in the for cycle
> I will obtain that the entries for each bin of the projection will
> be 256 .
>
> Bests,
>
> Melinda
>
>
>
>
>
>
>
>
> ---------- Forwarded message ----------
> From: Rene Brun <Rene.Brun_at_cern.ch>
> Date: Thu, Mar 13, 2008 at 2:25 PM
> Subject: Re: [ROOT] Projection of a histograms.....again...
> To: Melinda Siciliano <mellybinda_at_gmail.com>
> Cc: Lorenzo Moneta <lorenzo.moneta_at_cern.ch>, Root <roottalk_at_lxbuild091.cern.ch
> >
>
>
> Melinda,
>
> Why would you expect 256 entries per bin, given the fact that you fill
> each cell with a random number between 0 and 10 ?
> Lorenzo, please could you follow this discussion?
>
> Rene
>
> Melinda Siciliano wrote:
> > Dear Rene,
> >
> > Thanks a lot! Now the problem of the total number of the entries is
> > fixed. But Now I have another problem: If I compare the number of
> > entries I expect (in this case, 256 for each bin) with the number I
> > obtain from the loop, I obtain less effective entries. How can I
> > resolve it?
> >
> > #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();
> > Double_t number=0;
> > for(Int_t i=1;i<=256;i++)
> > {
> > for(Int_t j=1;j<=256;j++)
> > {
> > while(number==0){
> > number= 10*random->Rndm();
> > cout<<number<<endl;
> > }
> > histo->Fill(i-1.5,j-1.5,number);
> > number=0;
> > }
> > }
> >
> > Int_t countentx=0;
> > //Int_t countenty=0;
> > Int_t countenty=0;
> > Int_t count0=0;
> > for(Int_t i=1;i<=histo->GetXaxis()->GetNbins();i++){
> > if(countenty!=0) countenty=0;
> > for(Int_t j=1;j<=histo->GetYaxis()->GetNbins();j++)
> > {
> > Double_t content=histo->GetBinContent(i,j);
> > if(content!=0)
> > {
> > countenty=countenty+1;
> > //countentx=countentx+countenty;
> > }
> > else
> > if(content==0)
> > {
> > countenty=countenty+0;
> > count0++;
> > //countentx=countentx+0;
> > }
> > }
> > cout<<"bin = "<<i<<"\t entries = "<<countenty<<"\tzero
> "<<count0<<endl;
> > countentx=countentx+countenty;
> > count0=0;
> > }
> > cout<<"total ="<<countentx<<endl;
> > gStyle->SetPalette(1);
> > TCanvas *canvas =new TCanvas("canvas","canvas");
> > canvas->cd();
> > histo->Draw("colz");
> > canvas->Update();
> >
> > TH1D *px = histo->ProjectionX();
> > Double_t nentries =px->GetEntries();
> >
> > TCanvas *canvas2 =new TCanvas("canvas2","canvas2");
> > canvas2->cd();
> > px->Draw();
> > canvas2->Update();
> >
> > //TH1D *histo2=new TH1D("histo2","histo2",256,-0.5,255.5 );
> > 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);
> > cout<<"bin= "<<bin<<"\ty= "<<y <<"\te= "<<e <<"\teffe=
> "<<effe<<endl;
> >
> > px->SetBinContent(bin,effe);
> > px->SetBinError(bin,0);
> >
> > //histo2->Fill(double(bin)-1.5,effe);
> > //histo2->SetBinError(bin,0);
> > }
> > px->SetEntries(nentries);
> > /*
> > TCanvas *canvas3 =new TCanvas("canvas3","canvas3");
> > canvas3->cd();
> > histo2->Draw();
> > canvas3->Update();
> > */
> > TCanvas *canvas4 =new TCanvas("canvas4","canvas4");
> > canvas4->cd();
> > px->Draw();
> > canvas4->Update();
> >
> > }
> >
> >
> > Thanks,
> >
> > Melinda
> >
> > On Thu, Mar 13, 2008 at 8:34 AM, Rene Brun <Rene.Brun_at_cern.ch
> > <mailto:Rene.Brun_at_cern.ch>> wrote:
> >
> > Melinda,
> >
> > The call to hist.SetBinContent increases the number of entries
> by
> > 1. In
> > your case your call this
> > function 256 times, so you get 256 additional entries. See the
> fix
> > below
> >
> > Rene Brun
> >
> > TCanvas *canvas =new TCanvas("canvas","canvas");
> > canvas->cd();
> > histo->Draw("colz");
> > canvas->Update();
> > gStyle->SetPalette(1);
> > TH1D *px = histo->ProjectionX();
> > Double_t nentries = px->GetEntries(); //<==================
> > 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);
> > }
> > px->SetEntries(nentries); //<===================
> >
> > TCanvas *canvas2 =new TCanvas("canvas2","canvas2");
> > canvas2->cd();
> > px->Draw();
> > canvas2->Update();
> >
> >
> > Melinda Siciliano wrote:
> > > Hi,
> > >
> > > I make an error copying effe=(y*y)/(e*e), but the problem of
> the
> > > entries remain......Sorry....
> > >
> > > 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 bin
> > >
> > > }
> > >
> > > }
> > >
> > > 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 Wed, Mar 12, 2008 at 11:15 AM, Melinda Siciliano
> > > <mellybinda_at_gmail.com <mailto:mellybinda_at_gmail.com>
> > <mailto:mellybinda_at_gmail.com <mailto:mellybinda_at_gmail.com>>>
> wrote:
> > >
> > > 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 bin
> > >
> > > }
> > >
> > > }
> > >
> > > 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 <mailto:lorenzo.moneta_at_cern.ch>
> > <mailto:lorenzo.moneta_at_cern.ch <mailto: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 <mailto:Rene.Brun_at_cern.ch>
> > >> <mailto:Rene.Brun_at_cern.ch
> <mailto: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
> > >>
> > >>
> > >
> > >
> > >
> >
> >
>
>
Received on Thu Mar 13 2008 - 17:24:29 CET