Add a useful package (from Source forge) for octave

[CreaPhase.git] / octave_packages / statistics-1.1.3 / unifstat.m

diff --git a/octave_packages/statistics-1.1.3/unifstat.m b/octave_packages/statistics-1.1.3/unifstat.m
new file mode 100644 (file)
index 0000000..6023d87
--- /dev/null
+++ b/octave_packages/statistics-1.1.3/unifstat.m
@@ -0,0 +1,122 @@
+## Copyright (C) 2006, 2007 Arno Onken <asnelt@asnelt.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/>.
+
+## -*- texinfo -*-
+## @deftypefn {Function File} {[@var{m}, @var{v}] =} unifstat (@var{a}, @var{b})
+## Compute mean and variance of the continuous uniform distribution.
+##
+## @subheading Arguments
+##
+## @itemize @bullet
+## @item
+## @var{a} is the first parameter of the continuous uniform distribution
+##
+## @item
+## @var{b} is the second parameter of the continuous uniform distribution
+## @end itemize
+## @var{a} and @var{b} must be of common size or one of them must be scalar
+## and @var{a} must be less than @var{b}
+##
+## @subheading Return values
+##
+## @itemize @bullet
+## @item
+## @var{m} is the mean of the continuous uniform distribution
+##
+## @item
+## @var{v} is the variance of the continuous uniform distribution
+## @end itemize
+##
+## @subheading Examples
+##
+## @example
+## @group
+## a = 1:6;
+## b = 2:2:12;
+## [m, v] = unifstat (a, b)
+## @end group
+##
+## @group
+## [m, v] = unifstat (a, 10)
+## @end group
+## @end example
+##
+## @subheading References
+##
+## @enumerate
+## @item
+## Wendy L. Martinez and Angel R. Martinez. @cite{Computational Statistics
+## Handbook with MATLAB}. Appendix E, pages 547-557, Chapman & Hall/CRC,
+## 2001.
+##
+## @item
+## Athanasios Papoulis. @cite{Probability, Random Variables, and Stochastic
+## Processes}. McGraw-Hill, New York, second edition, 1984.
+## @end enumerate
+## @end deftypefn
+
+## Author: Arno Onken <asnelt@asnelt.org>
+## Description: Moments of the continuous uniform distribution
+
+function [m, v] = unifstat (a, b)
+
+  # Check arguments
+  if (nargin != 2)
+    print_usage ();
+  endif
+
+  if (! isempty (a) && ! ismatrix (a))
+    error ("unifstat: a must be a numeric matrix");
+  endif
+  if (! isempty (b) && ! ismatrix (b))
+    error ("unifstat: b must be a numeric matrix");
+  endif
+
+  if (! isscalar (a) || ! isscalar (b))
+    [retval, a, b] = common_size (a, b);
+    if (retval > 0)
+      error ("unifstat: a and b must be of common size or scalar");
+    endif
+  endif
+
+  # Calculate moments
+  m = (a + b) ./ 2;
+  v = ((b - a) .^ 2) ./ 12;
+
+  # Continue argument check
+  k = find (! (-Inf < a) | ! (a < b) | ! (b < Inf));
+  if (any (k))
+    m(k) = NaN;
+    v(k) = NaN;
+  endif
+
+endfunction
+
+%!test
+%! a = 1:6;
+%! b = 2:2:12;
+%! [m, v] = unifstat (a, b);
+%! expected_m = [1.5000, 3.0000, 4.5000, 6.0000, 7.5000, 9.0000];
+%! expected_v = [0.0833, 0.3333, 0.7500, 1.3333, 2.0833, 3.0000];
+%! assert (m, expected_m, 0.001);
+%! assert (v, expected_v, 0.001);
+
+%!test
+%! a = 1:6;
+%! [m, v] = unifstat (a, 10);
+%! expected_m = [5.5000, 6.0000, 6.5000, 7.0000, 7.5000, 8.0000];
+%! expected_v = [6.7500, 5.3333, 4.0833, 3.0000, 2.0833, 1.3333];
+%! assert (m, expected_m, 0.001);
+%! assert (v, expected_v, 0.001);