Add a useful package (from Source forge) for octave

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

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+## Copyright (C) 2006 Muthiah Annamalai <muthiah.annamalai@uta.edu>
+##
+## 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} {} shannonfanoenco (@var{hcode},@var{dict})
+## 
+## Returns the Shannon Fano encoded signal using @var{dict}.
+## This function uses a @var{dict} built from the @code{shannonfanodict}
+## and uses it to encode a signal list into a shannon fano code.
+## Restrictions include a signal set that strictly belongs  in the
+## @code{range [1,N]} with @code{N=length(dict)}. Also dict can only be
+## from the @code{shannonfanodict()} routine.
+## An example use of @code{shannonfanoenco} is
+##
+## @example
+## @group
+##          hd=shannonfanodict(1:4,[0.5 0.25 0.15 0.10])
+##          shannonfanoenco(1:4,hd) #  [   0   1   0   1   1   0   1   1   1   0]
+## @end group
+## @end example
+## @end deftypefn
+## @seealso{shannonfanodeco, shannonfanodict}
+##
+
+function sf_code=shannonfanoenco(sig,dict)
+  if nargin < 2
+    error('usage: huffmanenco(sig,dict)');
+  end
+  if (max(sig) > length(dict)) || ( min(sig) < 1)
+    error("signal has elements that are outside alphabet set ...
+       Cannot encode.");
+  end
+  sf_code=[dict{sig}];
+  return
+end
+%! 
+%! assert(shannonfanoenco(1:4, shannonfanodict(1:4,[0.5 0.25 0.15 0.10])),[   0   1   0   1   1   0   1   1   1   0],0)
+%!