--- /dev/null
+## 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} {} shannonfanodict (@var{symbols},@var{symbol_probabilites})
+##
+## Returns the code dictionary for source using shanno fano algorithm.
+## Dictionary is built from @var{symbol_probabilities} using the shannon
+## fano scheme. Output is a dictionary cell-array, which
+## are codewords, and correspond to the order of input probability.
+##
+## @example
+## @group
+## CW=shannonfanodict(1:4,[0.5 0.25 0.15 0.1]);
+## assert(redundancy(CW,[0.5 0.25 0.15 0.1]),0.25841,0.001)
+## shannonfanodict(1:5,[0.35 0.17 0.17 0.16 0.15])
+## shannonfanodict(1:8,[8 7 6 5 5 4 3 2]./40)
+## @end group
+## @end example
+## @end deftypefn
+## @seealso{shannonfanoenc, shannonfanodec}
+##
+function cw_list=shannonfanodict(symbol,P)
+
+ if nargin < 2
+ error('Usage: shannonfanodict(symbol,P); see help');
+ end
+
+ DMAX=length(P);
+ S=1:DMAX;
+
+ if(sum(P)-1.000 > 1e-7)
+ error('Sum of probabilities must be 1.000');
+ end
+#
+#FIXME: Is there any other way of doing the
+#topological sort? Insertion sort is bad.
+#
+#Sort the probability list in
+#descending/non-increasing order.
+#Using plain vanilla insertion sort.
+#
+ for i=1:DMAX
+ for j=i:DMAX
+
+ if(P(i) < P(j))
+
+ #Swap prob
+ t=P(i);
+ P(i)=P(j);
+ P(j)=t;
+
+ #Swap symb
+ t=S(i);
+ S(i)=S(j);
+ S(j)=t;
+ end
+
+ end
+ end
+
+
+ #Now for each symbol you need to
+ #create code as first [-log p(i)] bits of
+ #cumulative function sum(p(1:i))
+ #
+ #printf("Shannon Codes\n");
+ #data_table=zeros(1,DMAX);
+ cw_list={};
+
+ for itr=1:DMAX
+ if(P(itr)~=0)
+ digits=ceil(-log2(P(itr))); #somany digits needed.
+ else
+ digits=0; #dont assign digits for zero probability symbols.
+ end
+
+ Psum = sum([0 P](1:itr)); #Cumulative probability
+ s=[];
+ for i=1:digits;
+ Psum=2*Psum;
+ if(Psum >= 1.00)
+ s=[s 1];
+ Psum=Psum-1.00;
+ else
+ s=[s 0];
+ end
+ end
+ cw_list{itr}=s;
+ end
+
+ #re-arrange the list accroding to input prob list.
+ cw_list2={};
+ for i=1:length(cw_list)
+ cw_list2{i}=cw_list{S(i)};
+ end
+ cw_list=cw_list2;
+
+ return;
+end
+
+%!shared CW,P
+%!test
+%! P = [0.5 0.25 0.15 0.1];
+%! assert(shannonfanodict(1:4,P),{[0],[1 0],[1 1 0],[1 1 1 0]})
+%!