update packages

[CreaPhase.git] / octave_packages / m / general / prepad.m

diff --git a/octave_packages/m/general/prepad.m b/octave_packages/m/general/prepad.m
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+## Copyright (C) 1994-2012 John W. Eaton
+##
+## This file is part of Octave.
+##
+## Octave 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.
+##
+## Octave 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 Octave; see the file COPYING.  If not, see
+## <http://www.gnu.org/licenses/>.
+
+## -*- texinfo -*-
+## @deftypefn  {Function File} {} prepad (@var{x}, @var{l})
+## @deftypefnx {Function File} {} prepad (@var{x}, @var{l}, @var{c})
+## @deftypefnx {Function File} {} prepad (@var{x}, @var{l}, @var{c}, @var{dim})
+## Prepend the scalar value @var{c} to the vector @var{x} until it is of length
+## @var{l}.  If @var{c} is not given, a value of 0 is used.
+##
+## If @code{length (@var{x}) > @var{l}}, elements from the beginning of
+## @var{x} are removed until a vector of length @var{l} is obtained.
+##
+## If @var{x} is a matrix, elements are prepended or removed from each row.
+##
+## If the optional argument @var{dim} is given, operate along this
+## dimension.
+## @seealso{postpad, cat, resize}
+## @end deftypefn
+
+## Author: Tony Richardson <arichard@stark.cc.oh.us>
+## Created: June 1994
+
+function y = prepad (x, l, c, dim)
+
+  if (nargin < 2 || nargin > 4)
+    print_usage ();
+  endif
+
+  if (nargin < 3 || isempty (c))
+    c = 0;
+  else
+    if (! isscalar (c))
+      error ("prepad: third argument must be empty or a scalar");
+    endif
+  endif
+
+  nd = ndims (x);
+  sz = size (x);
+  if (nargin < 4)
+    ## Find the first non-singleton dimension.
+    (dim = find (sz > 1, 1)) || (dim = 1);
+  else
+    if (!(isscalar (dim) && dim == fix (dim))
+        || !(1 <= dim && dim <= nd))
+      error ("prepad: DIM must be an integer and a valid dimension");
+    endif
+  endif
+
+  if (! isscalar (l) || l < 0)
+    error ("prepad: second argument must be a positive scaler");
+  endif
+
+  if (dim > nd)
+    sz(nd+1:dim) = 1;
+  endif
+
+  d = sz (dim);
+
+  if (d >= l)
+    idx = repmat ({':'}, nd, 1);
+    idx{dim} = d-l+1:d;
+    y = x(idx{:});
+  else
+    sz (dim) = l - d;
+    y = cat (dim, c * ones (sz), x);
+  endif
+
+endfunction
+
+%!error prepad ();
+%!error prepad (1);
+%!error prepad (1,2,3,4,5);
+%!error prepad ([1,2], 2, 2,3);
+
+%!assert (prepad ([1,2], 4), [0,0,1,2]);
+%!assert (prepad ([1;2], 4), [0;0;1;2]);
+
+%!assert (prepad ([1,2], 4, 2), [2,2,1,2]);
+%!assert (prepad ([1;2], 4, 2), [2;2;1;2]);
+
+%!assert (prepad ([1,2], 2, 2, 1), [2,2;1,2]);
+
+## FIXME -- we need tests for multidimensional arrays.