[Numpy-discussion] strange behavior of ravel() and flatnonzero() on matrix

braingateway braingateway@gmail....
Wed Nov 3 18:04:07 CDT 2010


>>> aa=matrix([[-1, 2, 0],[0, 0, 3]])
>>> aa
matrix([[-1, 2, 0],
[ 0, 0, 3]])
>>> aa.nonzero()
(matrix([[0, 0, 1]], dtype=int64), matrix([[0, 1, 2]], dtype=int64))
*********OK*********
>>> npy.nonzero(aa.flat)
(array([0, 1, 5], dtype=int64),)
*********OK*********
>>> flatnonzero(aa)
matrix([[0, 0, 0]], dtype=int64)
*******This is Wrong**********
If I convert aa to an ndarray, it is OK then
aaa=asarray(aa)
>>> flatnonzero(aaa)
array([0, 1, 5], dtype=int64)

Then I figure it out that it might be induced by the behavior of ravel()
>>> aaa.shape
(2L, 3L)
>>> aaa.ravel().shape
(6L,)
>>> aa.ravel()
matrix([[-1, 2, 0, 0, 0, 3]])
>>> _.shape
(1L, 6L)
Why not make ravel() behaviors consistent under both ndarray and matrix
contexts?
Or make different flatnonzero() for the matrix context?
m.ravel().nonzero()[1]# for matrix
a.ravel().nonzero()[0]# for ndarray



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