Re: [ublas] from vector to bandex matrix

From: James N. Knight (nate_at_[hidden])
Date: 2007-02-23 15:31:07

Preben Hagh Strunge Holm wrote:
> Hi everyone
>
> Is there an easy way to go from a vector to a diagonal matrix 
> (bandex_matrix)?
>
>
> / Preben

I posted something about this a while ago.  You can download the file here
http://www.cs.colostate.edu/~nate/tutorial/diagonal_from_vector.hpp

Basically, this defines a special diagonal_vector_adaptor type and 
provides functions
diag and diagm.

The diagonal_vector_adaptor is a matrix expression allowing a vector to 
be viewed as the diagonal of a square matrix with zeros in all off 
diagonal elements.

diagm - creates a diagonal_vector_adaptor from a vector. 

diag - returns the diagonal of a matrix as a matrix_vector_slice so that 
the diagonal can be used as a vector.

Perhaps there is a better way, or the code can be improved in some way.

Hope this helps.

James