Adding TH2D in a loop

Newbie
1

Dear All,

I hope this question fits in the Newbie section. I have several root files which contain a TH2D histogram with exactly the same number of bins (basically it is the same histogram but filled with different data in each root file). I want to produce a single plot out of all of them. I am initializing an empty histogram and then adding the others to it. For obvious reasons (different binning) my code does not run but I want to avoid to change specific histogram and then loop over the others. Is there any workaround this? I am using PyROOT for this. My code is this one:

    for folder in folders:
        h_ph_2D_sum = TH2D()
        # Looping over all the root files in subdirectory
        for root_file in rootfile_dict[folder]:
            tmp_file = TFile(folder + root_file)  # Getting root file
            h_ph_2D_sum.Add(tmp_file.Get("h_2D"))

the error code is then:

Info in <TH2D::Add>: Attempt to add histograms with different number of bins - trying to use TH1::Merge
Error in <Merge>: Cannot merge histograms - limits are inconsistent:
 first:  (1, 0.000000, 1.000000), second: h_2D (128, 0.500000, 1280.500000)

I understand the error but I do not know any other solution apart from initializing the histogram to the correct number of bins.

Thanks in advance,
Arturo

2

Yes that what you should do.
You can simply get this information from the stored histograms.

3

Hi,
Thanks for the reply.
So, there is not other workaround this?

4

I do not see what is the penalty doing that ?

5

You’re right I just have to initialize with one histogram and the run my loop over the others.
Thank you