Re: R: help on Octave

[Martin Helm]

Am 27.06.2012 16:15, schrieb Pierpaolo:
>
> Hi,
>
> I followed your advice and now, using sparse matrix, I saved a lot of
> memory.
>
> But now with sparse matrix I get
>
> “warning: matrix singular to machine precision, rcond = 1
>
> warning: attempting to find minimum norm solution”
>
> evaluating this code:
>
> [L,U]=lu(A);
>
> C=U\(L\(B));
>
> where A,B are sparse matrix
>
> What does it mean?
>
> With A,B full matrix I have not this warning
>
> Thanks a lot
>
> Pierpaolo
>
It means what it says the matrix is not of full rank.
Maybe you made an error when assembling the sparse matrix, can you show
the part of the code you use now to create A?