A way to compute a 2d histogram

Nicolas Champavert nicolas.champavert at obs.univ-lyon1.fr
Wed Oct 25 06:56:04 CDT 2006


Hi,

    there is a problem when using this patch of numpy.histogram2d.
I've tried:
    a=pylab.rand(10)
    numpy.histogram2d(a,a)
and there is an exception (exceptions.AttributeError) in 
numpy.histogramdd function called by numpy.histogram2d.
But numpy.histogram2d(a,a,bins=[10,10]) works.
So I've tried to use directly numpy.histogramdd function:
    numpy.histogramdd([a,a])
and it works.
I've looked at the histogram2d code:
    try:
        N = len(bins)
    except TypeError:
        N = 1
        bins = [bins]
I think the last line (bins = [bins]) have to be deleted because if  you 
do so, numpy.histogram2d(a,a) works.
Or maybe the good think to do is:
try:
        N = len(bins)
    except TypeError:
        N = 1
        bins = 2*[bins]


Nicolas

David Huard a écrit :
> Xavier,
> Here is the patch against svn. Please report any bug. I haven't had 
> the time to test it extensively, something that should be done before 
> commiting the patch to the repo. I'd appreciate your feedback.
>
> David
>
> 2006/10/24, David Huard <david.huard at gmail.com 
> <mailto:david.huard at gmail.com>>:
>
>     Hi Xavier,
>
>     You could tweak histogram2d to do what you want, or you could give
>     me a couple of days and I'll do it and let you know. If you want
>     to help, you could write a test using your particular application
>     and data.
>
>     David
>
>
>
>
>      
>
>
>
>
>
>
>     2006/10/24, Xavier Gnata < gnata at obs.univ-lyon1.fr
>     <mailto:gnata at obs.univ-lyon1.fr>>:
>
>         Hi,
>
>         I have a set of 3 1D large arrays.
>         The first 2 one stand for the coordinates of particules and
>         the last one
>         for their masses.
>         I would like to be able to plot this data ie to compute a 2D
>         histogram
>         summing the masses in each bin.
>         I cannot find a way to do that without any loop on the indices
>         resulting
>         too a very slow function.
>
>         I'm looking for an elegant way to do that with numpy (or
>         scipy??) function.
>
>         For instance, scipy.histogram2d cannot do the job because it
>         only counts
>         the number of samples in each bin.
>         There is no way to deal with weights.
>
>         Xavier.
>
>
>         --
>         ############################################
>         Xavier Gnata
>         CRAL - Observatoire de Lyon
>         9, avenue Charles André
>         69561 Saint Genis Laval cedex
>         Phone: +33 4 78 86 85 28
>         Fax: +33 4 78 86 83 86
>         E-mail: gnata at obs.univ-lyon1.fr <mailto:gnata at obs.univ-lyon1.fr>
>         ############################################
>
>
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