Add a useful package (from Source forge) for octave

[CreaPhase.git] / octave_packages / communications-1.1.1 / gen2par.m

diff --git a/octave_packages/communications-1.1.1/gen2par.m b/octave_packages/communications-1.1.1/gen2par.m
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+## Copyright (C) 2003 David Bateman
+##
+## This program 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 3 of the License, or (at your option) any later
+## version.
+##
+## This program 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
+## this program; if not, see <http://www.gnu.org/licenses/>.
+
+## -*- texinfo -*-
+## @deftypefn {Function File} {@var{par} =} gen2par (@var{gen})
+## @deftypefnx {Function File} {@var{gen} =} gen2par (@var{par})
+##
+## Converts binary generator matrix @var{gen} to the parity chack matrix
+## @var{par} and visa-versa. The input matrix must be in standard form.
+## That is a generator matrix must be k-by-n and in the form [eye(k) P]
+## or [P eye(k)], and the parity matrix must be (n-k)-by-n and of the
+## form [eye(n-k) P'] or [P' eye(n-k)].
+##
+## @end deftypefn
+## @seealso{cyclgen,hammgen}
+
+function par = gen2par (gen)
+
+  if (nargin != 1)
+    usage (" par = gen2par (gen)");
+  endif
+
+  [gr, gc] = size(gen);
+
+  if (gr > gc)
+    error ("gen2par: input matrix must be in standard form");
+  endif
+
+  ## Identify where is the identity matrix
+  if (isequal(gen(:,1:gr),eye(gr)))
+    par = [gen(:,gr+1:gc)', eye(gc-gr)];
+  elseif (isequal(gen(:,gc-gr+1:gc),eye(gr)))
+    par = [eye(gc-gr), gen(:,1:gc-gr)'];
+  else
+    error ("gen2par: input matrix must be in standard form");
+  endif
+
+endfunction