[Numpy-discussion] arrray/matrix nonzero() type

[Nicolas Rougier]

Hi again,

I  have a problem with the nonzero() function for matrix.

The following test program:

import numpy, scipy.sparse

Z = numpy.zeros((10,10))
Z[0,0] = Z[1,1] = 1

i = Z.nonzero()
print i
Zc = scipy.sparse.coo_matrix((Z[i],i))

Z = numpy.matrix(Z)
i = Z.nonzero()
print i
Zc = scipy.sparse.coo_matrix((Z[i],i))


gives me:

(array([0, 1]), array([0, 1]))
(matrix([[0, 1]]), matrix([[0, 1]]))
Traceback (most recent call last):
   File "test.py", line 13, in <module>
     Zc = scipy.sparse.coo_matrix((Z[i],i))
   File "/Volumes/Data/Local/lib/python2.6/site-packages/scipy/sparse/ 
coo.py", line 179, in __init__
     self._check()
   File "/Volumes/Data/Local/lib/python2.6/site-packages/scipy/sparse/ 
coo.py", line 194, in _check
     nnz = self.nnz
   File "/Volumes/Data/Local/lib/python2.6/site-packages/scipy/sparse/ 
coo.py", line 187, in getnnz
     raise ValueError('row, column, and data arrays must have rank 1')
ValueError: row, column, and data arrays must have rank 1


Is that the intended behavior ? How can I use nonzero with matrix to  
build the coo one ?

Nicolas