Re: diag octave command into cc file

[Michael Creel]

Riccardo Corradini wrote:
> I would like to use command diag into cc
> Is there a simple instruction like DiagMatrix to indicate the vector and 
> the exact diagonal?
> How is possible to do for oct files?
> Thanks a lot in advance
Hi Riccardo,
I saw your message on the PK forum, but I'm answering here since the 
question is octave-related. The code
-------------------------
#include <oct.h>
#include <octave/parse.h>
DEFUN_DLD(KalmanInn_trans, args, ,"KalmanInn_trans.cc: C++ version for 
increased speed")
{
        octave_value_list f_args, f_return;
        
        // extract the arguments
        ColumnVector parameter = args(0).column_vector_value();
        int which_diagonal = args(1).int_value();
        f_args(1) = which_diagonal;
        f_args(0) = parameter;

        f_return(0)=feval("diag", f_args);

        return f_return;
}
---------------------------------------
does what you need, I think. The output is:

Welcome to MPITB
octave:1> a = rand(3,1)
a =

  0.87025
  0.67221
  0.89550

octave:2> KalmanInn_trans(a,2)
ans =
(
  [1] =

    0.00000  0.00000  0.87025  0.00000  0.00000
    0.00000  0.00000  0.00000  0.67221  0.00000
    0.00000  0.00000  0.00000  0.00000  0.89550
    0.00000  0.00000  0.00000  0.00000  0.00000
    0.00000  0.00000  0.00000  0.00000  0.00000

)
octave:3>


This is an example of how to call an Octave function from an .oct 
function. There's no speedup in the way the matrix is created, though, 
the "diag" code is the same as if it were called directly from the 
interpreter.

Cheers, Michael