--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main/info-theory/inst/narysource.m	Fri Nov 10 07:06:40 2006 +0000
@@ -0,0 +1,72 @@
+## Copyright (C) 2006, October, 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 2 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, write to the Free Software
+## Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+
+## -*- texinfo -*-
+## @deftypefn {Function File} {} narysource (@var{probability_dist},@var{n_order})
+##
+## This function creates a N-ary order source using the given
+## @var{probability_dist}  (as a column vector) of a 1-order source
+## building a probability distribution of size
+## len(@var{probability_dist})^@var{order}. Basically
+## if you have X-symbol distribution with a N-ary source then we have,
+## in the resultant N-ary source with a X^N symbols. The function is equivalent
+## to the definitions of a q-ary order source.
+##
+## @example
+## @group
+##  pdist=[1 2 3 4]./10;
+##  ndist = narysource(pdist,2)
+##        @result{}  [ 0.010000   0.020000   0.030000   0.040000   0.020000 0.040000   0.060000   0.080000   0.030000   0.060000    0.090000   0.120000   0.040000   0.080000   0.120000   0.160000]
+## @end group
+## @end example
+## @end deftypefn
+## @seealso{entropy}
+
+function opdist=narysource(pdist,order)
+  if(nargin < 2)
+    error('usage: ndist=narysource(pdist,order_n);')
+  end
+
+## #Method 1
+##  opdist=pdist;
+##  for idx=1:(order-1)
+##    L=length(opdist);
+##    ndist=[];
+##    for idy=1:L
+##      ndist=[ndist opdist(idy)*[pdist]];
+##    end
+##    opdist=ndist;
+##  end
+##
+
+## tic; narysource([1:4]./10,4); toc
+## tic; narysource([1:4]./10,10);toc
+
+## #Method 2
+  L=length(pdist);
+  opdist=pdist;## 1XN
+  pdist=pdist';## Nx1
+  for idx=2:order
+    opdist=pdist*opdist;## Nx1 * 1XN^k
+    opdist=reshape(opdist,1,L^idx);## 1xN^(k+1)
+  end
+
+  return
+end
+%!
+%!assert(narysource([1:4]./10,2),[ 0.010000   0.020000   0.030000   0.040000   0.020000 0.040000   0.060000   0.080000   0.030000   0.060000    0.090000   0.120000   0.040000   0.080000   0.120000   0.160000],1e-5);
+%!
+