Re: Concatonation of Matrices in octave API HOW?

[Stefan van der Walt]

Hi John

First, create an ND array of the appropriate size, then add your
result matrices.

   int nr_results = 10;
   int rows = 5;
   int cols = 5;

   NDArray nda(dim_vector(rows, cols, nr_results));
   Array<int> dim(3,0);

   for (int i = 0; i < nr_results; i++) {
       // generate a matrix
       Matrix A(rows, cols, 0);
       A(0,0) = i;

       // append the matrix
       dim(2) = i;
       nda = nda.concat(A, dim);
   }

This code should give

ans(:,:,1) =

  0  0  0  0  0
  0  0  0  0  0
  0  0  0  0  0
  0  0  0  0  0
  0  0  0  0  0

ans(:,:,2) =

  1  0  0  0  0
  0  0  0  0  0
  0  0  0  0  0
  0  0  0  0  0
  0  0  0  0  0

etc.

Regards
Stefan

On Wed, Jun 08, 2005 at 08:06:08PM -0500, John Weatherwax wrote:
> Hello,
>  I have several matrices, each one represents the solutions to a system of 
> PDE's at several timesteps.  I currently get each one by a call to a 
> fortran subroutine that integrates the PDE from time t_{n} to time t_{n+1}. 
> I would like to be able to "concatonate" these matrices into a NDArray (or 
> similar) structure to then pass out of the C++ gateway routine I have 
> written that interfaces with the fortran code but I cannot seem to be able 
> to figure out how to do this.  What I need is something like:
> 
> NDArray uAll;
> for( int i=1; i<=nTimesteps; i++){
>  Matrix uOneStep( numberOfPDEs, numberOfGridPts );
>  double* uOneStepP = uOneStep.fortran_vec();
>  F77_FUNC(pdecode,PDECODE)(uOneStepP,... other args...)
>  uAll.insert( uOneStep )
> }
> return uAll;
> 
> Thus uAll would have its "page" dimension each timeslice.  This may not be 
> the best way to do this.  Any "other" method to get this multidemisional 
> information out would be helpful too.
> 
> TIA,
> 
> Wax



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