Finding Nonzero Elements in a Sparse Matrix

Nick Vatamaniuc vatamane at gmail.com
Tue Nov 7 17:40:18 EST 2006


The function you might want is nonzero() or flatnonzero()

>>> from numpy import *

>>> a=array([ [1,2],[0,4] ])

>>> a
array([[1, 2],
           [0, 4]])

>>> flatnonzero(a)
array([0, 1, 3])

nonzero() will return the a sequence of index arrays of non zero
elements
flatnonzero()  returns the non-zero elements of the flattened version
of the array.

Cheers,
Nick Vatamaniuc



deLenn wrote:
> Hi,
>
> Does scipy have an equivalent to Matlab's 'find' function, to list the
> indices of all nonzero elements in a sparse matrix?
> 
> Cheers.




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