1 ## Copyright (C) 1993-2012 John W. Eaton
3 ## This file is part of Octave.
5 ## Octave is free software; you can redistribute it and/or modify it
6 ## under the terms of the GNU General Public License as published by
7 ## the Free Software Foundation; either version 3 of the License, or (at
8 ## your option) any later version.
10 ## Octave is distributed in the hope that it will be useful, but
11 ## WITHOUT ANY WARRANTY; without even the implied warranty of
12 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 ## General Public License for more details.
15 ## You should have received a copy of the GNU General Public License
16 ## along with Octave; see the file COPYING. If not, see
17 ## <http://www.gnu.org/licenses/>.
20 ## @deftypefn {Function File} {} trace (@var{A})
21 ## Compute the trace of @var{A}, @code{sum (diag (@var{A}))}.
26 function y = trace (A)
33 error ("trace: only valid on 2-D objects");
36 elseif (any (size (A) == 1))
44 %!assert(trace ([1, 2; 3, 4]) == 5);
45 %!assert(trace ([1, 2; 3, 4; 5, 6]) == 5);
46 %!assert(trace ([1, 3, 5; 2, 4, 6]) == 5);
47 %!assert(trace ([]), 0);
48 %!assert(trace (randn(1,0)), 0);
52 %!error <only valid on 2-D objects> trace(reshape(1:9,[1,3,3]));