Add a useful package (from Source forge) for octave

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

diff --git a/octave_packages/communications-1.1.1/randsrc.m b/octave_packages/communications-1.1.1/randsrc.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{b} = } randsrc (@var{n})
+## @deftypefnx {Function File} {@var{b} = } randsrc (@var{n},@var{m})
+## @deftypefnx {Function File} {@var{b} = } randsrc (@var{n},@var{m},@var{alphabet})
+## @deftypefnx {Function File} {@var{b} = } randsrc (@var{n},@var{m},@var{alphabet},@var{seed})
+##
+## Generate a matrix of random symbols. The size of the matrix is
+## @var{n} rows by @var{m} columns. By default @var{m} is equal to @var{n}.
+##
+## The variable @var{alphabet} can be either a row vector or a matrix with 
+## two rows. When @var{alphabet} is a row vector the symbols returned in
+## @var{b} are chosen with equal probability from @var{alphabet}. When
+## @var{alphabet} has two rows, the second row determines the probabilty
+## with which each of the symbols is chosen. The sum of the probabilities
+## must equal 1. By default @var{alphabet} is [-1 1].
+##
+## The variable @var{seed} allows the random number generator to be seeded
+## with a fixed value. The initial seed will be restored when returning.
+## @end deftypefn
+
+## 2003 FEB 13
+##   initial release
+
+function b = randsrc (n, m, alphabet, seed)
+
+  switch (nargin)
+    case 0,
+      m = 1;
+      n = 1;
+      alphabet = [-1,1];
+      seed = Inf;
+    case 1,
+      m = n;
+      alphabet = [-1,1];
+      seed = Inf;
+    case 2,
+      alphabet = [-1,1];
+      seed = Inf;
+    case 3,
+      seed = Inf;      
+    case 4,
+    otherwise
+      usage ("b = randsrc (n, [m, [alphabet, [seed]]])");
+  endswitch
+
+  ## Check alphabet
+  [ar,ac] = size (alphabet);
+  if (ac == 1)
+    b = alphabet (1, 1) * ones (n, m);
+    return;
+  endif
+
+  if (ar == 1)
+    prob = [1:ac] / ac;
+  elseif (ar == 2)
+    prob = alphabet(2,:);
+    alphabet = alphabet(1,:);
+    if (abs(1-sum(prob)) > eps)
+      error ("randsrc: probabilities must added up to one");
+    endif
+    prob = cumsum(prob);
+  else
+    error ("randsrc: alphabet must have 1 or 2 rows");
+  endif
+  
+  ## Check seed;
+  if (!isinf (seed))
+    old_seed = rand ("seed");
+    rand ("seed", seed);
+  endif
+  
+  ## Create indexes with the right probabilities
+  tmp = rand (n, m);
+  b = ones (n, m);
+  for i = 1:ac-1 
+    b = b + (tmp > prob(i));
+  end
+
+  ## Map the indexes to the symbols
+  b = alphabet(b);
+  
+  ## BUG: the above gives a row vector for some reason. Force what we want
+  b = reshape(b, n, m);
+    
+  ## Get back to the old
+  if (!isinf (seed))
+    rand ("seed", old_seed);
+  endif
+
+endfunction
+
+%!shared n, alph1, alph2, seed, a1, a2, a3, a4, a5, a6
+%!    n = 10; alph1 = [0,1;0.3,0.7]; alph2 = ['a','b']; seed = 1; 
+%!    a1 = randsrc(n); a2 = randsrc(n,n);
+%!    a3 = randsrc(n,n,alph1); a4 = randsrc(n,n,alph2); 
+%!    a5 = randsrc(n,n,alph1,seed); a6 = randsrc(n,n,alph1,seed);
+
+%!error randsrc (n,n,n,n,n);
+%!assert (size(a1) == [n, n] && size(a2) == [n, n]);
+%!assert (max ([a1(:); a2(:)]) <= 1 && min([a1(:); a2(:)]) >= -1);
+%!assert (size(a3) == [n, n] && size(a4) == [n, n]);
+%!assert (max (a3(:)) <= 1 && min(a3(:)) >= 0);
+%!assert (max(toascii(a4(:))) <= toascii('b'))
+%!assert (max(toascii(a4(:))) >= toascii('a'))
+%!assert (a5(:) == a6(:));