Add a useful package (from Source forge) for octave

[CreaPhase.git] / octave_packages / quaternion-2.0.0 / @quaternion / mtimes.m

diff --git a/octave_packages/quaternion-2.0.0/@quaternion/mtimes.m b/octave_packages/quaternion-2.0.0/@quaternion/mtimes.m
new file mode 100644 (file)
index 0000000..8252f08
--- /dev/null
+++ b/octave_packages/quaternion-2.0.0/@quaternion/mtimes.m
@@ -0,0 +1,43 @@
+## Copyright (C) 2010   Lukas F. Reichlin
+##
+## 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 -*-
+## Matrix multiplication of two quaternions. Used by Octave for "q1 * q2".
+
+## Author: Lukas Reichlin <lukas.reichlin@gmail.com>
+## Created: May 2010
+## Version: 0.1
+
+function a = mtimes (a, b)
+
+  if (! isa (a, "quaternion"))
+    a = quaternion (a);
+  endif
+
+  if (! isa (b, "quaternion"))
+    b = quaternion (b);
+  endif
+
+  w = a.w*b.w - a.x*b.x - a.y*b.y - a.z*b.z;
+  x = a.y*b.z - a.z*b.y + a.w*b.x + a.x*b.w;
+  y = a.z*b.x - a.x*b.z + a.w*b.y + a.y*b.w;
+  z = a.x*b.y - a.y*b.x + a.w*b.z + a.z*b.w;
+
+  a.w = w;
+  a.x = x;
+  a.y = y;
+  a.z = z;
+
+endfunction