/usr/share/octave/packages/tsa-4.2.7/detrend.m is in octave-tsa 4.2.7-1build1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 | function [X,T]=detrend(t,X,p)
% DETREND removes the trend from data, NaN's are considered as missing values
%
% DETREND is fully compatible to previous Matlab and Octave DETREND with the following features added:
% - handles NaN's by assuming that these are missing values
% - handles unequally spaced data
% - second output parameter gives the trend of the data
% - compatible to Matlab and Octave
%
% [...]=detrend([t,] X [,p])
% removes trend for unequally spaced data
% t represents the time points
% X(i) is the value at time t(i)
% p must be a scalar
%
% [...]=detrend(X,0)
% [...]=detrend(X,'constant')
% removes the mean
%
% [...]=detrend(X,p)
% removes polynomial of order p (default p=1)
%
% [...]=detrend(X,1) - default
% [...]=detrend(X,'linear')
% removes linear trend
%
% [X,T]=detrend(...)
%
% X is the detrended data
% T is the removed trend
%
% see also: SUMSKIPNAN, ZSCORE
% Copyright (C) 1995, 1996 Kurt Hornik <Kurt.Hornik@ci.tuwien.ac.at>
% $Id: detrend.m 11693 2013-03-04 06:40:14Z schloegl $
% Copyright (C) 2001,2007 by Alois Schloegl <a.schloegl@ieee.org>
% This function is part of the TSA-toolbox
% http://pub.ist.ac.at/~schloegl/matlab/tsa/
% Copyright (C) 1997, 1998, 2008 by Alois Schloegl <a.schloegl@ieee.org>
%
% This program 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 3 of the License, or
% (at your option) any later version.
%
% This program 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 this program. If not, see <http://www.gnu.org/licenses/>.
if (nargin == 1)
p = 1;
X = t;
t = [];
elseif (nargin == 2)
if strcmpi(X,'constant'),
p = 0;
X = t;
t = [];
elseif strcmpi(X,'linear'),
p = 1;
X = t;
t = [];
elseif ischar(X)
error('unknown 2nd input argument');
elseif all(size(X)==1),
p = X;
X = t;
t = [];
else
p = 1;
end;
elseif (nargin == 3)
if ischar(X),
warning('input arguments are not supported');
end;
elseif (nargin > 3)
fprintf (1,'usage: detrend (x [, p])\n');
end;
% check data, must be in culomn order
[m, n] = size (X);
if (m == 1)
X = X';
r=n;
else
r=m;
end
% check time scale
if isempty(t),
t = (1:r).'; % make time scale
elseif ~all(size(t)==size(X))
t = t(:);
end;
% check dimension of t and X
if ~all(size(X,1)==size(t,1))
fprintf (2,'detrend: size(t,1) must same as size(x,1) \n');
end;
% check the order of the polynomial
if (~(all(size(p)==1) & (p == round (p)) & (p >= 0)))
fprintf (2,'detrend: p must be a nonnegative integer\n');
end
if (nargout>1) , % needs more memory
T = zeros(size(X))+nan;
%T=repmat(nan,size(X)); % not supported by Octave 2.0.16
if (size(t,2)>1), % for multiple time scales
for k=1:size(X,2),
idx=find(~isnan(X(:,k)));
b = (t(idx,k) * ones (1, p + 1)) .^ (ones (length(idx),1) * (0 : p));
T(idx,k) = b * (b \ X(idx,k));
end;
else % if only one time scale is used
b = (t * ones (1, p + 1)) .^ (ones (length(t),1) * (0 : p));
for k=1:size(X,2),
idx=find(~isnan(X(:,k)));
T(idx,k) = b(idx,:) * (b(idx,:) \ X(idx,k));
%X(idx,k) = X(idx,k) - T(idx,k); % 1st alternative implementation
%X(:,k) = X(:,k) - T(:,k); % 2nd alternative
end;
end;
X = X-T; % 3nd alternative
if (m == 1)
X = X';
T = T';
end
else % needs less memory
if (size(t,2)>1), % for multiple time scales
for k = 1:size(X,2),
idx = find(~isnan(X(:,k)));
b = (t(idx,k) * ones (1, p + 1)) .^ (ones (length(idx),1) * (0 : p));
X(idx,k) = X(idx,k) - b * (b \ X(idx,k));
end;
else % if only one time scale is used
b = (t * ones (1, p + 1)) .^ (ones (length(t),1) * (0 : p));
for k = 1:size(X,2),
idx = find(~isnan(X(:,k)));
X(idx,k) = X(idx,k) - b(idx,:) * (b(idx,:) \ X(idx,k));
end;
end;
if (m == 1)
X = X';
end
end;
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