Re: Projections of 2D histograms
Rene Brun (Rene.Brun@cern.ch)
Tue, 20 May 1997 09:41:41 +0200
Christopher Conner wrote:
>
> Is there a way to make "Slix" or "banx" or "proj" on 2D
> histograms. I see that the Profile Class can handle this but I
> see no constuctor that take a 2D histogram and a range in y and
> fill the profile from the 2D histogram.
>
> I found a way to extract bin values from a 1D histogram
> but I don't see how to do it for a 2D histogram. How is this done?
>
> It looks like 2D histograms inherit from 1D histograms but
> then what is the bin number corresponding to binx=5 and biny=10?
>
We do not have a function making a projection of a 2-D histogram
into a Profile histogram or a 1-D histogram.
We are planning to add this functionality coupled with the dynamic
projection using a slider.
However, if you use a TNtuple/TTree, this functionality is already
there.
To extract bin values from a 2-D, use
TH1::GetCellContent(Int_t binx, Int_t biny)
Uou can also use:
Int_t bin = TH1::GetBin(Int_t binx, Int_t biny, Int_t binz)
The GetBin function returns a global bin number.
Then you can use teh normal GetBinContent(bin).
Rene Brun