[Numpy-discussion] histogram for discrete data

[josef.pktd at gmail.com]

2009/12/6 Ernest Adrogué <eadrogue at gmx.net>:
> Hi,
>
> A few weeks ago there was a discussion about a
> histogram_discrete() function --sorry for starting a new
> thread but I have lost the mails.
>
> Somebody pointed out that bincount() already can be used
> to histogram discrete data (except that it doesn't work
> with negative values).
>
> I have just discovered a function in scipy.stats called
> itemfreq() that does handle negative values.
>
> In [17]: scipy.stats.itemfreq([-1,-1,0,5])
> Out[17]:
> array([[-1.,  2.],
>       [ 0.,  1.],
>       [ 5.,  1.]])

bincount is a fast c function, stats.itemfreq uses a slow python loop.
The latter should be very slow for large arrays.

stats.itemfreq works also on floats, but not on strings (which should be a bug).

Josef


> Bye.
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