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annotate scripts/signal/detrend.m @ 3457:e031284eea27

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[project @ 2000-01-19 08:49:56 by jwe]
author jwe
date Wed, 19 Jan 2000 08:50:14 +0000
parents 858695b3ed62
children 38c61cbf086c
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1 ## Copyright (C) 1995, 1996 Kurt Hornik
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2 ##
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3 ## This program is free software; you can redistribute it and/or modify
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4 ## it under the terms of the GNU General Public License as published by
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5 ## the Free Software Foundation; either version 2, or (at your option)
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6 ## any later version.
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7 ##
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8 ## This program is distributed in the hope that it will be useful, but
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9 ## WITHOUT ANY WARRANTY; without even the implied warranty of
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10 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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11 ## General Public License for more details.
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12 ##
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13 ## You should have received a copy of the GNU General Public License
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14 ## along with this file. If not, write to the Free Software Foundation,
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15 ## 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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16
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17 ## -*- texinfo -*-
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18 ## @deftypefn {Function File} {} detrend (@var{x}, @var{p})
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19 ## If @var{x} is a vector, @code{detrend (@var{x}, @var{p})} removes the
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20 ## best fit of a polynomial of order @var{p} from the data @var{x}.
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21 ##
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22 ## If @var{x} is a matrix, @code{detrend (@var{x}, @var{p})} does the same
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23 ## for each column in @var{x}.
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24 ##
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25 ## The second argument is optional. If it is not specified, a value of 1
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26 ## is assumed. This corresponds to removing a linear trend.
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27 ## @end deftypefn
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28
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29 ## Author: KH <Kurt.Hornik@ci.tuwien.ac.at>
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30 ## Created: 11 October 1994
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31 ## Adapted-By: jwe
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32
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33 function y = detrend (x, p)
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34
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35 if (nargin == 1)
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36 p = 1;
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37 elseif (nargin == 2)
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38 if (! (is_scalar (p) && p == round (p) && p >= 0))
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39 error ("detrend: p must be a nonnegative integer");
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40 endif
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41 else
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42 usage ("detrend (x, p)");
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43 endif
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44
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45 [m, n] = size (x);
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46 if (m == 1)
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47 x = x';
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48 endif
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49
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50 r = rows (x);
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51 b = ((1 : r)' * ones (1, p + 1)) .^ (ones (r, 1) * (0 : p));
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52 y = x - b * (b \ x);
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53
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54 if (m == 1)
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55 y = y';
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56 endif
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57
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58 endfunction