update packages

[CreaPhase.git] / octave_packages / m / linear-algebra / trace.m

diff --git a/octave_packages/m/linear-algebra/trace.m b/octave_packages/m/linear-algebra/trace.m
new file mode 100644 (file)
index 0000000..ea14fad
--- /dev/null
+++ b/octave_packages/m/linear-algebra/trace.m
@@ -0,0 +1,52 @@
+## Copyright (C) 1993-2012 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} {} trace (@var{A})
+## Compute the trace of @var{A}, @code{sum (diag (@var{A}))}.
+## @end deftypefn
+
+## Author: jwe
+
+function y = trace (A)
+
+  if (nargin != 1)
+    print_usage ();
+  endif
+
+  if (ndims (A) > 2)
+    error ("trace: only valid on 2-D objects");
+  elseif (isempty (A))
+    y = 0;
+  elseif (any (size (A) == 1))
+    y = A(1);
+  else
+    y = sum (diag (A));
+  endif
+
+endfunction
+
+%!assert(trace ([1, 2; 3, 4]) == 5);
+%!assert(trace ([1, 2; 3, 4; 5, 6]) == 5);
+%!assert(trace ([1, 3, 5; 2, 4, 6]) == 5);
+%!assert(trace ([]), 0);
+%!assert(trace (randn(1,0)), 0);
+%!
+%!error trace ();
+%!error trace (1, 2);
+%!error <only valid on 2-D objects> trace(reshape(1:9,[1,3,3]));