Re: [matplotlib-devel] hist doesn't work with 2D arrays

[Andrew H. <HA...@no...>]

Ah - that makes sense. I guess I didn't catch that change in the release notes. Thanks again!

-----Original Message-----
From: Manuel Metz [mailto:mm...@as...]
Sent: 7 Jul 2008 11:49 AM
To: mat...@li...
Cc: Andrew Hawryluk
Subject: Re: [matplotlib-devel] hist doesn't work with 2D arrays


Andrew Hawryluk wrote:
> Hopefully this isn't old news for you. Since the 0.98 release, the histogram plot doesn't work properly with 2D arrays: it is quite slow and the output is wrong. Passing a flattened array produces the quick, correct output that we are accustomed to. Here is the test code I ran, and the attached image shows the output compared with the previous version.
> 
> import numpy as n
> import matplotlib.pyplot as p
> 
> a = n.random.normal(size=10000)
> a = a.reshape((100,100))   # make a 2D array of normally-distributed random numbers
> p.hist(a)
> 
> 
> Thanks for your work on matplotlib!

Hi Andrew,
   2D arrays are now treated differently. An (N,M) 2D array is 
interpreted as M data-sets with N elements each, e.g.

a = n.random.normal(size=10000)
a = a.reshape((1000,10))

is interpreted as 10 data-sets with 1000 elements each. See 
histogram_demo_extended.py in examples/pylab_examples.

To reproduce the old behaviour you should use pylab.hist(a.flat).

Manuel

> Andrew Hawryluk
> Calgary, Canada
>  <<hist-comparison.png>> 
> 
> 
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