[SciPy-user] Sparse matrices

David Grant david at dwavesys.com
Wed Nov 10 15:08:13 CST 2004


Travis Oliphant wrote:

> Nils Wagner wrote:
>
>> Hi all,
>>
>> from scipy import *
>> A = sparse.dok_matrix()
>>
>> for i in range(3):
>>  A[i,i] = 0.0+0.0j
>> # A[i,i] = 0.1+0.0j
>>
>> n,m = A.shape
>> print n,m
>> print A
>>
>>
>> n, m should be equal to 3, but this is only valid for non-zero entries.
>>
>> Am I missing something ?
>
>
> Entering a zero value into a sparse matrix causes no storage and 
> therefore no shape changes.  A remains an empty sparse matrix.   What 
> are you trying to do?
>
>
One thing that it is interesting.  These sparse arrays are dynamically 
allocated I assume?  In the PySparse package, arrays are dynamically 
allocated, but the shape must be set upon initialization.  It looks like 
you've made a more flexible package here.



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