Histo changes bin and entries when switching to log scale

ROOT
1

I am observing a strange behavior when switching a canvas to logx (graphically from TCanvas).

I am plotting two histos(with same nbins and ends) together. When I plot with linear scale, they look correct (see picture). The beginning/end of each bin appears in the same place for both histos, and the red one is never over the blue one as it should.

Switching to log, it looks like the red histo is higher than the blue one in some bins (meaning it’s not at the same values). Moreover, it looks the beginning and end of bins are not matching across the two histos.
Any idea why, and how to ensure consistency when setting log scale?

OscSpecLog
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3

OscSpecLin
OscSpecLin698×474 2.65 KB

4

It looks like the bins are shifted by 1 between the two histos when I select log scale!

5

Hi,
it could be a numerical issue caused by switching on the log-scale. I would need a small example reproducing this, if you can post for example a ROOT file with the two histograms and the macro showing this, it will be good

Thank you

Lorenzo

6

We will need a macro (and data) reproducing the problem.
Are the histograms starting at 0 on X ?

7

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