[SciPy-User] sparse matrix construction question

Christopher Mutel cmutel@gmail....
Fri Apr 13 15:16:57 CDT 2012

One easy way is to construct a new CSR matrix, extending on the numpy
arrays "data", "indptr", and "indices" from the original matrix.
Because the I can never quite figure out the CSR format, I usually
convert to a COO matrix, where it is easy to extend the "data", "row",
and "col" numpy arrays. This can be slower, but is definitely much
faster than the LIL matrix conversion.

See e.g. http://stackoverflow.com/questions/6844998/is-there-an-efficient-way-of-concatenating-scipy-sparse-matrices


On Fri, Apr 13, 2012 at 9:47 PM, Eric Carlson <ecarlson@eng.ua.edu> wrote:
> Hello,
> I have a million row sparse matrix that can be created almost
> instantaneously using spdiags and csr format. I need to add one column
> and one row, and insert some nonzeros at various (symmetric) locations
> in the row and columns. I can easily accomplish this using lil format,
> but this increases the construction to around 20 seconds from about .05
> seconds.
> I can probably work something out in fortran + f2py pretty easily, but ...
> Any python sparse matrix wizards out there with some tips?
> Cheers,
> Eric Carlson
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