Re: nnz and char

[David Bateman]

Andy Adler wrote:

> On Tue, 31 Jan 2006, David Bateman wrote:
> > This patch is not quite right. The problem is that there are two 
> methods
> > in Sparse<T> for the number of non-zero elements. These are "nnz" and
> > "nonzero". "nnz" returns the size of data and ridx, while nonzero
> > returns "cidx[ncol]"... For matlab compatiablity for sparse matrices,
> > Fnnz should return "cidx[ncol]" rather than the size of ridx and data,
> > which is why the old Fnnz in sparse.cc used the "nonzero" method of
> > Sparse<T>..
>
> David,
>
> I'm embarassed to admit this, but I can't figure out what you said.
>
> Could you explain what the difference is between cidx[ncol] and
> length( ridx )?
> --
> Andy Adler <address@hidden> 1(613)562-5800x6218
In a compressed column sparse storage the actual number of elements 
stored in the matrix is cidx[ncol] where as the amount of memory 
actually allocated to store the elements might differ from this value. 
Within octave this doesn't cause a problem as the two always match. 
However, I have had matrices imported from matlab where this was not the 
case and that caused me much pain...

D.

--
David Bateman                                address@hidden
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