1 ## Copyright (C) 1995-2012 Friedrich Leisch
3 ## This file is part of Octave.
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
7 ## the Free Software Foundation; either version 3 of the License, or (at
8 ## your option) any later version.
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12 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 ## General Public License for more details.
15 ## You should have received a copy of the GNU General Public License
16 ## along with Octave; see the file COPYING. If not, see
17 ## <http://www.gnu.org/licenses/>.
20 ## @deftypefn {Function File} {} hurst (@var{x})
21 ## Estimate the Hurst parameter of sample @var{x} via the rescaled range
22 ## statistic. If @var{x} is a matrix, the parameter is estimated for
23 ## every single column.
26 ## Author: FL <Friedrich.Leisch@ci.tuwien.ac.at>
27 ## Description: Estimate the Hurst parameter
29 function H = hurst (x)
36 error ("hurst: X must not be a scalar");
38 x = reshape (x, length (x), 1);
44 w = cumsum (x - mean (x));
45 RS = (max(w) - min(w)) ./ s;
46 H = log (RS) / log (xr);