Re: About diagonal matrices

[Søren Hauberg]

lor, 21 02 2009 kl. 16:46 -0500, skrev John W. Eaton:
> Yes, I understand that it is convenient for many uses for diagonal
> and sparse matrices to have the properties you want.  But I'm also
> don't like having things like
> 
>   full_matrix == diag_matrix
> 
> yet
> 
>   diag_matrix * scalar != full_matrix * scalar
> 
> for some values of scalar.

I don't like this either. But I must say that I really like the reduced
memory usage that comes with the diagonal matrix type (this has already
saved me a couple of times). I guess I'm missing the obvious here, but
couldn't the diagonal matrix class be extended to have a variable that
holds the value of the non-diagonal elements of the matrix? Usually this
would be zero, but when the matrix is multiplied with NaN or divided
with zero, this value would change.

Soren