X-Git-Url: https://git.creatis.insa-lyon.fr/pubgit/?p=CreaPhase.git;a=blobdiff_plain;f=octave_packages%2Flinear-algebra-2.2.0%2F%40kronprod%2Ftrace.m;fp=octave_packages%2Flinear-algebra-2.2.0%2F%40kronprod%2Ftrace.m;h=75be2a52cbfabe879a208df641080064a0f72b77;hp=0000000000000000000000000000000000000000;hb=c880e8788dfc484bf23ce13fa2787f2c6bca4863;hpb=1705066eceaaea976f010f669ce8e972f3734b05

diff --git a/octave_packages/linear-algebra-2.2.0/@kronprod/trace.m b/octave_packages/linear-algebra-2.2.0/@kronprod/trace.m
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+++ b/octave_packages/linear-algebra-2.2.0/@kronprod/trace.m
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+## 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} trace (@var{KP})
+## Returns the trace of the Kronecker product @var{KP}.
+##
+## If @var{KP} is a Kronecker product of two square matrices, the trace is
+## computed as the product of the trace of these two matrices. Otherwise the
+## trace is computed by forming the full matrix.
+## @seealso{@@kronprod/det, @@kronprod/rank, @@kronprod/full}
+## @end deftypefn
+
+function retval = trace (KP)
+  if (nargin != 1)
+    print_usage ();
+  endif
+  
+  if (!isa (KP, "kronprod"))
+    error ("trace: input must be of class 'kronprod'");
+  endif
+  
+  if (issquare (KP.A) && issquare (KP.B))
+    retval = trace (KP.A) * trace (KP.B);
+  else
+    ## XXX: Can we do something smarter here? Using 'eig' or 'svd'?
+    retval = trace (full (KP));
+  endif
+endfunction