[Numpy-discussion] fast method to to count a particular value in a large matrix

Jerome Kieffer Jerome.Kieffer@esrf...
Sat Feb 4 14:42:48 CST 2012

On Sat, 4 Feb 2012 14:35:08 -0600
Benjamin Root <ben.root@ou.edu> wrote:

> no.unique() can return indices and reverse indices.  It would be trivial to
> histogram the reverse indices using np.histogram().

Even np.histogram(abc,unique_elem) or something like this. 
Works if unique_elem is ordered.

is 40x faster and gives the same result.

Jérôme Kieffer
Data analysis unit - ESRF

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