--- /dev/null
+## 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(:));