[SciPy-dev] better sparse slicing

[Robert Cimrman]

Nathan Bell wrote:
> I've expanded on Robert C's earlier efforts in improving the state of
> sparse slicing.
> 
> Previously you could do
> A[1]
> A[1:2]
> A[1:2,1]
> A[1:2,1:2]
> 
> Now you can do:
> A[[1,2]]
> A[1:2,[1,2]]
> A[[1,2],1:2]
> A[[1,2],[1,2]]

Great!

> and the all important:
> A[[1,2],:][:,[1,2]]

This needs some more range checking...

In [3]: a = sp.csr_matrix( [[1,0,1,0],[0,1,2,3]] )
In [5]: print a
   (0, 0)        1
   (0, 2)        1
   (1, 1)        1
   (1, 2)        2
   (1, 3)        3
In [6]: a[[1,2],:][:,[1,2]]
Segmentation fault

> 
> Currently this only works for csr_matrix (and not csc_matrix).  Once I
> trust my csr_matrix implementation I'll make csc_matrix work also.
> The above operations should mimic numpy.matrix exactly.

Many thanks for this, Nathan.

r.