Add a useful package (from Source forge) for octave

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

diff --git a/octave_packages/communications-1.1.1/randerr.m b/octave_packages/communications-1.1.1/randerr.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} = } randerr (@var{n})
+## @deftypefnx {Function File} {@var{b} = } randerr (@var{n},@var{m})
+## @deftypefnx {Function File} {@var{b} = } randerr (@var{n},@var{m},@var{err})
+## @deftypefnx {Function File} {@var{b} = } randerr (@var{n},@var{m},@var{err},@var{seed})
+##
+## Generate a matrix of random bit errors. The size of the matrix is
+## @var{n} rows by @var{m} columns. By default @var{m} is equal to @var{n}.
+## Bit errors in the matrix are indicated by a 1.
+##
+## The variable @var{err} determines the number of errors per row. By
+## default the return matrix @var{b} has exactly one bit error per row.
+## If @var{err} is a scalar, there each row of @var{b} has exactly this
+## number of errors per row. If @var{err} is a vector then each row has
+## a number of errors that is in this vector. Each number of errors has    
+## an equal probability. If @var{err} is a matrix with two rows, then 
+## the first row determines the number of errors and the second their
+## probabilities.
+##
+## 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 = randerr (n, m, err, seed)
+
+  switch (nargin)
+    case 0,
+      m = 1;
+      n = 1;
+      err = 1;
+      seed = Inf;
+    case 1,
+      m = n;
+      err = 1;
+      seed = Inf;
+    case 2,
+      err = 1;
+      seed = Inf;
+    case 3,
+      seed = Inf;      
+    case 4,
+    otherwise
+      usage ("b = randerr (n, [m, [err, [seed]]])");
+  endswitch
+
+  ## Check error vector
+  [ar,ac] = size (err);
+  if (ac == 1) 
+    if (ar > 1)
+      err = err';
+    endif
+  elseif ((ac > 1) && (ar != 1) && (ar != 2))
+    error ("randerr: err must be a scalar, vector or two row matrix");
+  endif
+  for i=1:ac
+    if (err(1,i) > m)
+      error ("randerr: illegal number of errors per row");
+    endif
+  end
+    
+  # Use randsrc to calculate the number of errors per row
+  nerrs = randsrc (n, 1, err, seed);
+  
+  # Now put to errors into place in the return matrix
+  b = zeros (n, m);
+  for i=1:n
+    if (nerrs(i) > 0)
+      if (nerrs(i) == 1)
+        indx = sort(randint(1,nerrs(i),m,seed));
+      else
+        do
+          indx = sort(randint(1,nerrs(i),m,seed));
+        until (! any(indx(1:nerrs(i)-1) == indx(2:nerrs(i))))
+      endif
+      b(i,indx+1) = ones(1,nerrs(i)); 
+    endif
+  end
+endfunction
+
+
+%!shared n, err1, err2, seed, a1, a2, a3, a4, a5, a6
+%!    n = 10; err1 = 2; err2 = [1,2;0.7,0.3] ; seed = 1; 
+%!    a1 = randerr(n); a2 = randerr(n,n);
+%!    a3 = randerr(n,n,err1); a4 = randerr(n,n,err2); 
+%!    a5 = randerr(n,n,err1,seed); a6 = randerr(n,n,err1,seed);
+
+%!error randerr (n,n,n,n,n);
+%!assert (size(a1) == [n, n] && size(a2) == [n, n]);
+%!assert (all (sum (a1.') == 1) && all (sum (a2.') == 1))
+%!assert (all((a1(:) == 1 | a1(:) == 0)) &&all((a2(:) == 1 | a2(:) == 0)))
+%!assert (size(a3) == [n, n] && size(a4) == [n, n]);
+%!assert (all (sum (a3.') == err1))
+%!assert (all((a3(:) == 1 | a3(:) == 0)))
+%!assert (all ((sum (a4.') == err2(1,1)) | (sum (a4.') == err2(1,2))))
+%!assert (all((a4(:) == 1 | a4(:) == 0)))
+%!assert (a5(:) == a6(:));