[Rivet] Question concerning histograms

[Andy Buckley]

On 21/09/11 12:38, Hendrik Hoeth wrote:
> Thus spake Martin Stoll (martin at particle.uni-karlsruhe.de):
>
>> (In fact I want to fill my histogram with the ratio of the entries of
>> two other ones.)
>
> If you want to divide two histograms, have a look e.g. at the finalize()
> method in STAR_2006_S6500200.cc.

Ah, I think I understand better now: you're doing a manual histogram 
division and trying to write the results (where the bin width factor has 
cancelled) into a *histogram*?

This idea of a histogram as a binned object whose values and errors can 
just be set to desired values is one of those great gifts that ROOT has 
given to the world! AIDA has two distinct data types for that -- a 
"histogram" has bin contents, heights, etc. based on its aggregated fill 
history, while a "data point set" is the thing whose x/y values and 
errors can be set arbitrarily.

So you can either set the divided values directly on a DPS obtained via 
bookDataPointSet(...), or (easier, or at least more standard) use the 
division method that Hendrik pointed at.

Hope that helps!
Andy

-- 
Dr Andy Buckley
SUPA Advanced Research Fellow
Particle Physics Experiment Group, University of Edinburgh

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