update packages

[CreaPhase.git] / octave_packages / m / sparse / speye.m

diff --git a/octave_packages/m/sparse/speye.m b/octave_packages/m/sparse/speye.m
new file mode 100644 (file)
index 0000000..5ccb418
--- /dev/null
+++ b/octave_packages/m/sparse/speye.m
@@ -0,0 +1,57 @@
+## Copyright (C) 2004-2012 David Bateman and Andy Adler
+##
+## 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} {@var{y} =} speye (@var{m})
+## @deftypefnx {Function File} {@var{y} =} speye (@var{m}, @var{n})
+## @deftypefnx {Function File} {@var{y} =} speye (@var{sz})
+## Return a sparse identity matrix.  This is significantly more
+## efficient than @code{sparse (eye (@var{m}))} as the full matrix
+## is not constructed.
+##
+## Called with a single argument a square matrix of size @var{m} by
+## @var{m} is created.  Otherwise a matrix of @var{m} by @var{n} is
+## created.  If called with a single vector argument, this argument
+## is taken to be the size of the matrix to create.
+## @end deftypefn
+
+function s = speye (m, n)
+  if (nargin == 1)
+    if (isvector (m) && length(m) == 2)
+      n = m(2);
+      m = m(1);
+    elseif (isscalar (m))
+      n = m;
+    else
+      error ("speye: invalid matrix dimension");
+    endif
+  else
+    if (! isscalar (m) || ! isscalar (n))
+      error ("speye: invalid matrix dimension");
+    endif
+  endif
+
+  lo = min ([m, n]);
+  s = sparse (1:lo, 1:lo, 1, m, n);
+endfunction
+
+%!assert(issparse(speye(4)))
+%!assert(speye(4),sparse(1:4,1:4,1))
+%!assert(speye(2,4),sparse(1:2,1:2,1,2,4))
+%!assert(speye(4,2),sparse(1:2,1:2,1,4,2))
+%!assert(speye([4,2]),sparse(1:2,1:2,1,4,2))