Re: [ROOT] 2d histogram: right number but wrong colour in col mode

From: Reinhardt Chamonal (chamonal@ph.ed.ac.uk)
Date: Sat Nov 06 2004 - 17:42:02 MET 

Here is a short version of the "script" 

TH2F *correl =new TH2F("Correlation", "MaPTM #3",64,0.5,64.5,64,0.5,64.5);
for(int i=1;i<=64;i++){    //pixel x
  for(int j=1;j<=64;j++){  //pixel y
 	Some calculatons
	for(int k=1;k<=ne;k++){ //loop over nb of entries 
	Some more calculations
        }
   float p=covXY/(sigmaX*sigmaY);
   correl->Fill(i,j,p);
  }
}

Thanks

On Sat, 6 Nov 2004, Rene Brun wrote:

> Reinhart,
> 
> Please send the shortest possible script illustrating your problem.
> 
> A priori, it looks like you are filling bins with values of i or/and j
> at the edge of the bin (precision problem). Instead, specify the bin 
> center.
> 
> Rene Brun
> 
> On 
> Sat, 
> 6 Nov 2004, Reinhardt Chamonal wrote:
> 
> > Hi,
> > 
> > I am using v4.00/01
> > I am filling a 2d histogram (wihtin a C porgram) , with:
> > correl->Fill(i,j,p);
> > where i and j are integers and p is a float.
> > Now my problem is that when I draw the histogram in col mode sometimes the 
> > color isn't right when my entry is 1, 1 being my maximum value. With a 
> > palette from blue to red, sometimes it would be blue and sometimes red 
> > eventhough the entry is one :(
> > Any idea of what I might be doing wrong ?
> > I have attached two pictures where the diagonal illustrates the problem.
> > 
> > Cheers
> >  
> > 
> > 
> > 
> > 
> 

-- 
------------------------------------------------------------
 Reinhardt CHAMONAL            The University of Edinburgh  
                               School of Physics 
 email: chamonal@ph.ed.ac.uk   King's Buildings, JCMB, 5301 
                               Mayfield Road                
 phone: +44-131-650 5307       Edinburgh, EH9 3JZ           
 
 web: http://www.ph.ed.ac.uk/~chamonal/
      http://www.reuh.ovh.org
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