[Numpy-discussion] question about histogram2d

David Huard david.huard@gmail....
Thu May 29 19:21:58 CDT 2008


Hi Darren,

If I remember correctly, the thinking under the current behavior is that it
preserves similarity of results with histogramdd, where the histogram is
oriented in the numpy order (columns, rows). I thought that making
histogram2d(x,y) return something different than histogramdd([x,y]) was
probably worst than satisfying the cartesian convention.

Regards,

David



2008/5/29 Darren Dale <darren.dale@cornell.edu>:

> I have a question about histogram2d. Say I do something like:
>
> import numpy
> from numpy import random
> import pylab
>
> x=random.rand(1000)-0.5
> y=random.rand(1000)*10-5
>
> xbins=numpy.linspace(-10,10,100)
> ybins=numpy.linspace(-10,10,100)
> h,x,y=numpy.histogram2d(x,y,bins=[xbins,ybins])
>
> pylab.imshow(h,interpolation='nearest')
> pylab.show()
>
> The output is attached. I think I would have expected the transpose of what
> numpy histogram2d returned, so the tight x distribution appears along the x
> axis in the image. Maybe I am thinking about this incorrectly, or there is
> a
> convention I am unfamiliar with. If the behavior is correct, could the
> docstring include a comment explaining the orientation of the histogram
> array?
>
> Thanks,
> Darren
>
> --
> Darren S. Dale, Ph.D.
> Staff Scientist
> Cornell High Energy Synchrotron Source
> Cornell University
> 275 Wilson Lab
> Rt. 366 & Pine Tree Road
> Ithaca, NY 14853
>
> darren.dale@cornell.edu
> office: (607) 255-3819
> fax: (607) 255-9001
> http://www.chess.cornell.edu
>
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