[SciPy-user] dimension mismatch error

[Dinesh B Vadhia]

I want to do a vector-matrix multiplication as follows:

 

z = y * A

 

... where y is a (1 x J) vector, A is a (I x J) Scipy (csr) Sparse matrix, and the resulting z a (1 x J) vector.

 

The calculation results in this dimension mismatch error:

 

Traceback (most recent call last):
  File " ... .py", line 260, in <module>
    ...

  File "C:\Python25\Lib\site-packages\scipy\sparse\base.py", line 350, in __rmul__
    return (self.transpose() * tr).transpose()
  File "C:\Python25\Lib\site-packages\scipy\sparse\base.py", line 299, in __mul__
    raise ValueError('dimension mismatch')
ValueError: dimension mismatch

 

Any ideas?

 

Dinesh

 

 

[David Cournapeau]

Dinesh B Vadhia wrote:
> I want to do a vector-matrix multiplication as follows:
>
> z = y * A
>
> ... where y is a (1 x J) vector, A is a (I x J) Scipy (csr) Sparse
> matrix, and the resulting z a (1 x J) vector.

Is y dimension (1xJ) a type or the actual dimension ? In that later
case, a ValueError is expected for matrix product :)

cheers,

David
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[josef...@gmail.com]

I guess this is the problem
It looks like, which multiplication is used, is defined by the order,
__rmult__, __mult__

>>> A = sparse.lil_matrix([[0.0,0,5,3],]).tocsr()
>>> A
<1x4 sparse matrix of type '<type 'numpy.float64'>'
with 2 stored elements in Compressed Sparse Row format>
>>> np.ones(4)*A

Traceback (most recent call last):

File "<pyshell#126>", line 1, in <module>
np.ones(4)*A
File "\Programs\Python25\Lib\site-packages\scipy\sparse\base.py",

line 350, in __rmul__
return (self.transpose() * tr).transpose()

File "\Programs\Python25\Lib\site-packages\scipy\sparse\base.py",

line 299, in __mul__
raise ValueError('dimension mismatch')
ValueError: dimension mismatch

>>> A*np.ones(4)
array([ 8.])

Josef