TH2:Divide number of entries

ROOT
1

I have a naive question. I have two TH2 histograms and I use Divide to get bin content of first histogram over the second one. The thing is I am not sure about the entry numbers of the created histogram.

In my case, first one has ~13M, second one has ~1200 events. After I divide them, I obtain the histo with ~6.5 entries. What’s the procedure of getting this result? That does not make sense to me.

2

Hi,

In case of some histogram operations, such as divisions, the number of entries do not make much sense. Normally if the histogram is not representing anymore counts, the returned summer of entries is computed using the effective entries, which is equal to (sum of bins content)^2/(sum of bins Error^2).

Best Regards

Lorenzo