Put custom errors


I would like to ask this - I have in a histo some function. How can I put “custom” error bars on this plot, ie not using the draw(“E”) options but errors with calculated values out of another calculation for example?

use TH1::SetBinError


Yes, I already have done this but without result…

Look this first plot - top is the ratios, while bottom is my custom errors (1.png) - seperate plots, to see, that the errors are really small numbers

Now, 2.png shows the result after a loop for the calcutation and the custom SetBinError - it looks like (don’t mind if you don’t see entries after 250GeV, I just runned this for fewer events)

[code]{for int i=0;i<20;i++){

Fraction->Fill(i40, fraction[i]);

After that, at the end, I do

It is obvious, if you compare 1.png with 2.pn, that the error bars are oversized, while I don’t even see the fraction bars from the 1.png plot…

Nevertheless, if I do Fraction->Draw(“E”); I get same exactly wrong plot…

Can you help me you with this?

Thanks in advance

Could you send the shortest possible RUNNING script reproducing your case?
For your code extract, I have the feeling that you are setting the error for the wrong bin number ::slight_smile:
First bin is bin 1, underflow bin is bin 0.


Thanks for the fast reply!

Well, actually, it is not easy at all to send a running script, as it reads a .h file, which reads some 100mb ntuple to produce this…Anyway, I tried to bypass the first 5 bins (ie i=6;i<20;i++ ) but this gives me the same oversized plot. Oh, the TH1F has 800 bins, and I tried several bin size, but always the same …

From your picture pn2g it looks like you are setting errors in a different bin where you Fill (see tiny errors next to the big errors) where the bin content is null and correct errors. To check my point, simply replace

Fraction->Fill(i*40, fraction[i]); by

Fraction->SetBinContent(i*40, fraction[i]);

This works!!!

Thanks a lot Rene!