[Numpy-discussion] [Newbie] Fast plotting

John Hunter jdh2358@gmail....
Wed Jan 7 10:14:44 CST 2009


On Wed, Jan 7, 2009 at 6:37 AM, Franck Pommereau
<pommereau@univ-paris12.fr> wrote:

> def f4 (x, y) :
>    """Jean-Baptiste Rudant <boogaloojb@yahoo.fr>
>
>    test 1 CPU times: 111.21s
>    test 2 CPU times: 13.48s
>
>    As Jean-Baptiste noticed, this solution is not very efficient (but
>    works almost of-the-shelf).
>    """
>    recXY = numpy.rec.fromarrays((x, x), names='x, y')
>    return matplotlib.mlab.rec_groupby(recXY, ('x',),
>                                       (('y', numpy.mean, 'y_avg'),))

This probably will have no impact on your tests, but this looks like a
bug.  You probably mean:

  recXY = numpy.rec.fromarrays((x, y), names='x, y')

Could you post the code you use to generate you inputs (ie what is x?)

I will look into trying some of the suggestions here to improve the
performance on rec_groupby.  One thing that slows it down is that it
supports an arbitrary number of keys -- eg groupby ('year', 'month')
-- whereas the examples above are using a single value lookup.

JDH


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