Re: [ROOT] sumw2 array

From: Rene Brun (Rene.Brun@cern.ch)
Date: Fri Nov 28 2003 - 18:38:37 MET


Hi Tommaso,

You can produce a TProfile2D histogram with:

tree->Draw("V:Y:X","","prof lego")

Rene Brun

Tommaso Chiarusi wrote:
> 
> dear rooters,
> 
> I have a TH2.
> I want to re-weight each bin according to the average of a
> variable with
> respect to the number of elements contained in each bin.
> 
> For example: if I have a tree with X Y and V leaves,
> by
> 
> tree->Draw("Y:X","V","lego");
> 
> I get a 3-D plot with for each bin, on the Z axis, the sum of the values
> related variable V over all the elements which occur in such bin.
> 
> Instead I would like to have an average of V for each bin.
> 
> I noticed  that it is possible to create a  structure (an array) of the
> square  of the bins' content with
> 
> TH1::Sumw2()
> 
> Now, do exist an option that authomatically performs
> what I want (by using somehow such weight-structure), or should I write it
> by myself?
> 
> Regards,
> Tommaso



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