1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
|
## Copyright (C) 1996 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 2, 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, write to the Free
## Software Foundation, 59 Temple Place - Suite 330, Boston, MA
## 02111-1307, USA.
## usage: sinc(x)
##
## Returns sin(pi*x)/(pi*x).
## Author: jwe
function result = sinc (x)
## We either need to set the do_fortran_indexing variable to "true"
## or use reshape to convert the input matrix to a vector, so that
## we can use find to determine the elements of x that equal zero.
## I prefer reshaping.
[nr, nc] = size(x);
nels = nr*nc;
x = reshape(x,nels,1);
## Set result to all ones initially.
result = ones(nels,1);
## Find non-zero elements in the input matrix.
i = find(x);
if (!isempty(i))
result(i) = sin(pi*x(i))./(pi*x(i));
endif
result = reshape(result,nr,nc);
endfunction
|
