Error computed by TH3

ROOT
1

Hello again

Comparing two plots one created as TH1F and another as projection of TH3F, the entries are identical as expected but the bin content is different. I attach two plots.

On looking at documentation, it says that the “effective entry” is calculated, I don’t understand why entry has to be recomputed in case I’m doing projection. I’m suspecting that this may be the reason for different errors but I’m not sure why this is the case. When filling the histograms, the entries are weighted, could this be the reason?
new.root (61 KB)

Picture 2.png692×470 8.11 KB


Picture 3.png691×468 3.64 KB

2

A problem was fixed in TH3::Project3D a few weeks ago.
Move to version 5.23/04

Rene

3

Hi Rene

I run with 5.23.04, the problem is not resolved.

Akira

4

I do not see any problem with 5.23/04. Are you really sure to run with this version?

Rene

5

Hi Rene

Indeed it seems that the errors are calculated correctly in the new version but entries and mean are different. If I do

f=TFile(“new.root”)
f.Get(“Mu_Pt_Eta_etcone20”).Project3D(‘y’).Draw()
f.Get(“Mu_Eta”).Draw()

I see that the histograms look the same but parameters are different.
new.root (61 KB)

6

Hello Akira,

currently the statistics information is calculated on the projected histogram from the information of the bin content.
It is true, that when no cuts are applied, we could use the original statistics from the TH3 histogram.
We will fix this for the next release,

Thank you for reporting this issue

Cheers

Lorenzo

7

I was wondering why recalculation is necessary but of course it makes sense if one is applying cuts. Thanks
Akira