Mercurial > hg > octave-lyh
annotate scripts/signal/fractdiff.m @ 11529:f98f925d8e5c
Add undocumented function erfcx to documentation.
| author | Rik <octave@nomad.inbox5.com> |
|---|---|
| date | Fri, 14 Jan 2011 11:59:59 -0800 |
| parents | fd0a3ac60b0e |
| children | 72c96de7a403 |
| rev | line source |
|---|---|
| 11523 | 1 ## Copyright (C) 1995-2011 Friedrich Leisch |
| 3426 | 2 ## |
| 3922 | 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 | |
| 7016 | 7 ## the Free Software Foundation; either version 3 of the License, or (at |
| 8 ## your option) any later version. | |
| 3426 | 9 ## |
| 3922 | 10 ## Octave is distributed in the hope that it will be useful, but |
| 3191 | 11 ## WITHOUT ANY WARRANTY; without even the implied warranty of |
| 12 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
| 3426 | 13 ## General Public License for more details. |
| 14 ## | |
| 3191 | 15 ## You should have received a copy of the GNU General Public License |
| 7016 | 16 ## along with Octave; see the file COPYING. If not, see |
| 17 ## <http://www.gnu.org/licenses/>. | |
| 3191 | 18 |
| 3449 | 19 ## -*- texinfo -*- |
| 20 ## @deftypefn {Function File} {} fractdiff (@var{x}, @var{d}) | |
| 3499 | 21 ## Compute the fractional differences @math{(1-L)^d x} where @math{L} |
| 22 ## denotes the lag-operator and @math{d} is greater than -1. | |
| 3449 | 23 ## @end deftypefn |
| 3426 | 24 |
| 3457 | 25 ## Author: FL <Friedrich.Leisch@ci.tuwien.ac.at> |
| 26 ## Description: Compute fractional differences | |
| 3426 | 27 |
| 3191 | 28 function retval = fractdiff (x, d) |
| 3426 | 29 |
| 7125 | 30 if (nargin != 2) |
| 31 print_usage (); | |
| 32 endif | |
| 33 | |
| 3191 | 34 N = 100; |
| 3426 | 35 |
| 4030 | 36 if (! isvector (x)) |
|
11472
1740012184f9
Use uppercase for variable names in error() strings to match Info documentation. Only m-files done.
Rik <octave@nomad.inbox5.com>
parents:
8920
diff
changeset
|
37 error ("fractdiff: X must be a vector"); |
| 3191 | 38 endif |
| 3426 | 39 |
| 4030 | 40 if (! isscalar (d)) |
|
11472
1740012184f9
Use uppercase for variable names in error() strings to match Info documentation. Only m-files done.
Rik <octave@nomad.inbox5.com>
parents:
8920
diff
changeset
|
41 error ("fractdiff: D must be a scalar"); |
| 3191 | 42 endif |
| 3426 | 43 |
| 44 | |
| 3191 | 45 if (d >= 1) |
| 46 for k = 1 : d | |
| 47 x = x(2 : length (x)) - x(1 : length (x) - 1); | |
| 48 endfor | |
| 49 endif | |
| 3426 | 50 |
| 3191 | 51 if (d > -1) |
| 3426 | 52 |
| 3191 | 53 d = rem (d, 1); |
| 3426 | 54 |
| 3191 | 55 if (d != 0) |
| 56 n = (0 : N)'; | |
| 57 w = real (gamma (-d+n) ./ gamma (-d) ./ gamma (n+1)); | |
| 58 retval = fftfilt (w, x); | |
| 59 retval = retval(1 : length (x)); | |
| 60 else | |
| 61 retval = x; | |
| 62 endif | |
| 3426 | 63 |
| 3191 | 64 else |
|
11472
1740012184f9
Use uppercase for variable names in error() strings to match Info documentation. Only m-files done.
Rik <octave@nomad.inbox5.com>
parents:
8920
diff
changeset
|
65 error ("fractdiff: D must be > -1"); |
| 3426 | 66 |
| 3191 | 67 endif |
| 3426 | 68 |
| 3191 | 69 endfunction |