# Copyright (C) 1996 John W. Eaton
# 
# This file is part of Octave.
# 
# Octave is free software; you can redistribute it and/or modify it
# under the terms of the GNU General Public License as published by the
# Free Software Foundation; either version 2, or (at your option) any
# later version.
# 
# Octave is distributed in the hope that it will be useful, but WITHOUT
# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
# FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
# for more details.
# 
# You should have received a copy of the GNU General Public License
# along with Octave; see the file COPYING.  If not, write to the Free
# Software Foundation, 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.

function [b, r] = deconv (y, a)

# usage: deconv (y, a)
#
# Deconvolve two vectors.
#
# [b, r] = deconv (y, a) solves for b and r such that 
#    y = conv(a,b) + r
#
# If y and a are polynomial coefficient vectors, b will contain the
# coefficients of the polynomial quotient and r will be a remander
# polynomial of lowest order.
#
# SEE ALSO: conv, poly, roots, residue, polyval, polyderiv,
# polyinteg 

# Written by Tony Richardson (amr@mpl.ucsd.edu) June 1994.

  if (nargin != 2)
    usage ("deconv (y, a)");
  endif

  if (is_matrix (y) || is_matrix (a))
    error("conv: both arguments must be vectors");
  endif

  la = length (a);
  ly = length (y);

  lb = ly - la + 1;

  if (ly > la)
    b = filter (y, a, [1, (zeros (1, ly - la))]);
  elseif (ly == la)
    b = filter (y, a, 1);
  else
    b = 0;
  endif

  b = polyreduce (b);

  lc = la + length (b) - 1;
  if (ly == lc)
    r = y - conv (a, b);
  else
    r = [(zeros (1, lc - ly)), y] - conv (a, b);
  endif

  r = polyreduce (r);

endfunction