|
245
|
1 # Copyright (C) 1993 John W. Eaton |
|
|
2 # |
|
|
3 # This file is part of Octave. |
|
|
4 # |
|
|
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 the |
|
|
7 # Free Software Foundation; either version 2, or (at your option) any |
|
|
8 # later version. |
|
|
9 # |
|
|
10 # Octave is distributed in the hope that it will be useful, but WITHOUT |
|
|
11 # ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
|
|
12 # FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
|
|
13 # for more details. |
|
|
14 # |
|
|
15 # You should have received a copy of the GNU General Public License |
|
|
16 # along with Octave; see the file COPYING. If not, write to the Free |
|
|
17 # Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. |
|
|
18 |
|
4
|
19 function retval = triu (x, k) |
|
|
20 |
|
|
21 # usage: triu (x, k) |
|
|
22 # |
|
|
23 # Return the upper triangular part of x above the k-th diagonal. If |
|
|
24 # the second argument is omitted, k = 0 is assumed. |
|
|
25 # |
|
|
26 # See also: tril, diag |
|
|
27 |
|
|
28 if (nargin > 0) |
|
|
29 [nr, nc] = size (x); |
|
|
30 retval = x; |
|
|
31 endif |
|
|
32 |
|
|
33 if (nargin == 1) |
|
|
34 k = 0; |
|
|
35 elseif (nargin == 2) |
|
|
36 max_nr_nc = max (nr, nc); |
|
|
37 if ((k > 0 && k > nc - 1) || (k < 0 && k < 1 - nr)) |
|
|
38 error ("triu: requested diagonal out of range") |
|
|
39 endif |
|
|
40 else |
|
|
41 error ("usage: triu (x [, k])"); |
|
|
42 endif |
|
|
43 |
|
|
44 for j = 1:nc |
|
|
45 for i = j+1-k:nr |
|
|
46 retval (i, j) = 0.0; |
|
|
47 endfor |
|
|
48 endfor |
|
|
49 |
|
|
50 endfunction |
