Differences in plots from histogram Fill() and tree Fill()?

Hello all,

I have got two plots.
One with just filling the histogram in a code


and the other by filling the same variable in a tree in another code.

std::vector<double> *electronPtarr; myTree->Branch("ePt","vector<double>",&electronPtarr); for(every event) { electronPtarr->clear(); electronPtarr->push_back(ePt); myTree->Fill(); }

I have made sure that both (tree variable and histo )are filled under same conditions
When I plotted these two these are giving same no. of entries, same area and they look similar except for some very minor binning differences.
I am attaching the two plots and the corresponding .C files which show the bin by bin enteries.

plot_treevariable.C & plot_treevariable.gif : tree variable files
plot_histofill.C and plot_histofill.gif : histogram files

Is that minor difference expected?

Thanks & Regards,
Shilpi Jain

plot_treevariable.C (5.25 KB)

plot_histoFill.C (6.34 KB)

It looks like you fill your histogram using a float (instead of double) variable.
If not, we need a complete running (but short) example reproducing the problem.


Thanks a lot for pointing that out :slight_smile:
All my histograms are float and tree variables are double!

Thanks & Regards,