update packages

[CreaPhase.git] / octave_packages / m / statistics / base / iqr.m

diff --git a/octave_packages/m/statistics/base/iqr.m b/octave_packages/m/statistics/base/iqr.m
new file mode 100644 (file)
index 0000000..45fda22
--- /dev/null
+++ b/octave_packages/m/statistics/base/iqr.m
@@ -0,0 +1,98 @@
+## 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} {} iqr (@var{x})
+## @deftypefnx {Function File} {} iqr (@var{x}, @var{dim})
+## Return the interquartile range, i.e., the difference between the upper
+## and lower quartile of the input data.  If @var{x} is a matrix, do the
+## above for first non-singleton dimension of @var{x}.
+##
+## If the optional argument @var{dim} is given, operate along this dimension.
+##
+## As a measure of dispersion, the interquartile range is less affected by
+## outliers than either @code{range} or @code{std}.
+## @seealso{range, std}
+## @end deftypefn
+
+## Author KH <Kurt.Hornik@wu-wien.ac.at>
+## Description: Interquartile range
+
+function y = iqr (x, dim)
+
+  if (nargin != 1 && nargin != 2)
+    print_usage ();
+  endif
+
+  if (! (isnumeric (x) || islogical (x)))
+    error ("iqr: X must be a numeric vector or matrix");
+  endif
+
+  nd = ndims (x);
+  sz = size (x);
+  nel = numel (x);
+  if (nargin != 2)
+    ## Find the first non-singleton dimension.
+    (dim = find (sz > 1, 1)) || (dim = 1);
+  else
+    if (!(isscalar (dim) && dim == fix (dim))
+        || !(1 <= dim && dim <= nd))
+      error ("iqr: DIM must be an integer and a valid dimension");
+    endif
+  endif
+
+  ## This code is a bit heavy, but is needed until empirical_inv
+  ## can take a matrix, rather than just a vector argument.
+  n = sz(dim);
+  sz(dim) = 1;
+  if (isa (x, 'single'))
+    y = zeros (sz, 'single');
+  else
+    y = zeros (sz);
+  endif
+  stride = prod (sz(1:dim-1));
+  for i = 1 : nel / n;
+    offset = i;
+    offset2 = 0;
+    while (offset > stride)
+      offset -= stride;
+      offset2++;
+    endwhile
+    offset += offset2 * stride * n;
+    rng = [0 : n-1] * stride + offset;
+
+    y(i) = diff (empirical_inv ([1/4, 3/4], x(rng)));
+  endfor
+
+endfunction
+
+
+%!assert (iqr (1:101), 50);
+%!assert (iqr (single(1:101)), single(50));
+
+%%!test
+%%! x = [1:100];
+%%! n = iqr (x, 0:10);
+%%! assert (n, [repmat(100, 1, 10), 1]);
+
+%!error iqr ();
+%!error iqr (1, 2, 3);
+%!error iqr (1);
+%!error iqr (['A'; 'B']);
+%!error iqr (1:10, 3);
+