update packages

[CreaPhase.git] / octave_packages / m / signal / detrend.m

diff --git a/octave_packages/m/signal/detrend.m b/octave_packages/m/signal/detrend.m
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+## Copyright (C) 1995-2012 Kurt Hornik
+##
+## 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 3 of the License, 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, see
+## <http://www.gnu.org/licenses/>.
+
+## -*- texinfo -*-
+## @deftypefn {Function File} {} detrend (@var{x}, @var{p})
+## If @var{x} is a vector, @code{detrend (@var{x}, @var{p})} removes the
+## best fit of a polynomial of order @var{p} from the data @var{x}.
+##
+## If @var{x} is a matrix, @code{detrend (@var{x}, @var{p})} does the same
+## for each column in @var{x}.
+##
+## The second argument is optional.  If it is not specified, a value of 1
+## is assumed.  This corresponds to removing a linear trend.
+##
+## The order of the polynomial can also be given as a string, in which case
+## @var{p} must be either @t{"constant"} (corresponds to @code{@var{p}=0}) or
+## @t{"linear"} (corresponds to @code{@var{p}=1}).
+## @seealso{polyfit}
+## @end deftypefn
+
+## Author: KH <Kurt.Hornik@wu-wien.ac.at>
+## Created: 11 October 1994
+## Adapted-By: jwe
+
+function y = detrend (x, p = 1)
+  ## Check input
+  if (nargin > 0 && isreal (x) && ndims (x) <= 2)
+    ## Check p
+    if (ischar (p) && strcmpi (p, "constant"))
+      p = 0;
+    elseif (ischar (p) && strcmpi (p, "linear"))
+      p = 1;
+    elseif (!isscalar (p) || p < 0 || p != fix (p))
+      error ("detrend: second input argument must be 'constant', 'linear' or a positive integer");
+    endif
+  else
+    error ("detrend: first input argument must be a real vector or matrix");
+  endif
+
+  [m, n] = size (x);
+  if (m == 1)
+    x = x';
+  endif
+
+  r = rows (x);
+  b = ((1 : r)' * ones (1, p + 1)) .^ (ones (r, 1) * (0 : p));
+  y = x - b * (b \ x);
+
+  if (m == 1)
+    y = y';
+  endif
+
+endfunction
+
+%!test
+%! N=32;
+%! x = (0:1:N-1)/N + 2;
+%! y = detrend(x);
+%! assert(all (all (abs (y) < 20*eps)));
+
+%!test
+%! N=32;
+%! t = (0:1:N-1)/N;
+%! x = t .* t + 2;
+%! y = detrend(x,2);
+%! assert(all (all (abs (y) < 30*eps)));
+
+%!test
+%! N=32;
+%! t = (0:1:N-1)/N;
+%! x = [t;4*t-3]';
+%! y = detrend(x);
+%! assert(all (all (abs (y) < 20*eps)));
+