[SciPy-dev] Dense to sparse operator

Nils Wagner nwagner at mecha.uni-stuttgart.de
Mon Feb 13 04:23:12 CST 2006


Nils Wagner wrote:
>Hi all,
>
>How can I "transform" a dense matrix into a sparse matrix in scipy ?
>
>Nils
> 
>
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>  
>>> A
array([[ 2. , -0.9,  0. ,  0. ],
       [-1.1,  2. , -0.9,  0. ],
       [ 0. , -1.1,  2. , -0.9],
       [ 0. ,  0. , -1.1,  2. ]])
>>> Asp=csc_matrix(A)
>>> Asp
<4x4 sparse matrix of type '<type 'float64scalar'>'
        with 10 stored elements (space for 10)
        in Compressed Sparse Column format>
>>> print Asp
  (0, 0)        2.0
  (1, 0)        -1.1
  (0, 1)        -0.9
  (1, 1)        2.0
  (2, 1)        -1.1
  (1, 2)        -0.9
  (2, 2)        2.0
  (3, 2)        -1.1
  (2, 3)        -0.9
  (3, 3)        2.0
>>> A.csc_matrix()
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
AttributeError: 'numpy.ndarray' object has no attribute 'csc_matrix'

The opposite way round works fine

>>> Asp.todense()
array([[ 2. , -0.9,  0. ,  0. ],
       [-1.1,  2. , -0.9,  0. ],
       [ 0. , -1.1,  2. , -0.9],
       [ 0. ,  0. , -1.1,  2. ]])

Nils


 





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