[Rivet] 2D Histograms in Rivet

[Sercan Sen]

Hi Hendrik, 

On Jul 31, 2012, at 10:48 PM, Hendrik Hoeth wrote:

> Hi Sercan,
> 
>> However, the color coding does not represent the number of events. As
>> you know rivet normalize the histograms to the bin sizes by default.
>> Therefore, what we see on the color scale is the values divided by
>> binsize_x * binsize_y . It depends what you want to show but would be
>> more meaningful if this 'by default' bin size normalization don't be
>> applied for 2D histograms.
> 
> A basic property of a histogram (in contrast to a bar chart) is that its
> values are invariant under changes of the binning. Your suggestion to
> count entries would destroy this property. What you would then get is
> not a histogram anymore. I am aware that this is not what you are used
> from ROOT.
> 
> If, for a specifiy use case, you need the sum of weights ("number of
> events"), you'll have to do what you did: Scale with the bin size.
> Either in the weight, or after the fact in the finalize() method.


yes, this works. 


> 
>> Anyway. I've tried a few tricks to get rid of this blue background in
>> Rivet 2D histograms, however, couldn't find an easy solution yet.
>> Before digging the codes I would like to ask you, if there is any
>> simple way to remove this blue background ?
>> 
>> ( btw, it's easy to understand from the histogram but let me tell you
>> that myValues are always > 0. and this blue region does not
>> corresponds to the 0 on the color scale. )
> 
> Oh yes, the blue area *does* correspond to the 0 on the color scale.
> You've never filled those bins, so the bin content *is* zero, and
> according to the color scale this means blue.
> 
> If you don't want to plot empty bins, you can delete them from the .dat
> file and then replot with make-plots. To do this, the easiest way is
> sed, i.e. something like
> 
> sed -i "/\t0.000000e+00\t0.000000e+00$/d" yourplotfile.dat


good to learn ! many thanks. 


> 
> Cheers,
> 
>    Hendrik
> 
> -- 
> Journalist: "Can you explain 5 sigma as 99.999something percent?"
> Fabiola G.: "Sure, that's 3*10^-7."
> (after the CERN Higgs seminar, 4 July 2012)