Add a useful package (from Source forge) for octave

[CreaPhase.git] / octave_packages / linear-algebra-2.2.0 / @kronprod / minus.m

diff --git a/octave_packages/linear-algebra-2.2.0/@kronprod/minus.m b/octave_packages/linear-algebra-2.2.0/@kronprod/minus.m
new file mode 100644 (file)
index 0000000..5bf47f1
--- /dev/null
+++ b/octave_packages/linear-algebra-2.2.0/@kronprod/minus.m
@@ -0,0 +1,52 @@
+## Copyright (C) 2010  Soren Hauberg
+## 
+## 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, 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 file.  If not, see <http://www.gnu.org/licenses/>.
+
+## -*- texinfo -*-
+## @deftypefn {Function File} minus (@var{a}, @var{a})
+## Return the difference between a Kronecker product and another matrix. This is performed
+## by forming the full matrix of both inputs and is as such a potential expensive
+## operation.
+## @seealso{minus, @@kronprod/plus}
+## @end deftypefn
+
+function retval = minus (M1, M2)
+  if (nargin != 2)
+    print_usage ();
+  endif
+  
+  if (!ismatrix (M1) || !ismatrix (M2))
+    error ("minus: both input arguments must be matrices");
+  endif
+  
+  if (!size_equal (M1, M2))
+    error ("minus: nonconformant arguments (op1 is %dx%d, op2 is %dx%d)",
+           rows (M1), columns (M1), rows (M2), columns (M2));
+  endif
+
+  ## XXX: Can we do something smarter here?
+  if (issparse (M1))
+    M1 = sparse (M1);
+  else
+    M1 = full (M1);
+  endif
+  
+  if (issparse (M2))
+    M2 = sparse (M2);
+  else
+    M2 = full (M2);
+  endif
+  
+  retval = M1 - M2;
+endfunction