From octave-sources-request at bevo dot che dot wisc dot edu Fri Dec 13 10:27:56 2002
Subject: Function to generate convolution matrix
From: Anand V <anand dot v at achayans dot com>
To: octave-sources at bevo dot che dot wisc dot edu
Date: Mon, 9 Dec 2002 08:03:52 -0600

Hi,
  I have written  a function to generate the convolution matrix using the toeplitz function.
I am appending it at the end. 

A convolution matrix is a matrix, formed from a vector, whose inner product with another vector is the convolution of the two vectors.

A = convmtx(c,n) where c is a length m column vector returns a matrix A of size (m+n-1)-by-n. The product of A and another column vector x of length n is the convolution of c with x.

A = convmtx(r,n) where r is a length m row vector returns a matrix A of size n-by-(m+n-1). The product of A and another row vector x of length n is the convolution of r with x.


# Function to get convolution matrix given a vector 'h' and length of x (n)

function retval = convmtx(h,n)

  if (nargin != 2)
    usage ("convmtx(h,n)");
  endif

nr = rows(h);
nc = columns(h);

if ( (nr > 1) && (nc > 1) )
  usage("'h' should be either a row or column vector");

else
if (nc == 1)
h = h.';
endif

r = [h,zeros(1,n-1)];
c = [1,zeros(1,n-1)];
endif

if (nr == 1)
retval = toeplitz(c,r);
endif

if (nc == 1)
retval = toeplitz(c,r).';
endif

endfunction



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