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scripts/statistics/distributions/wblcdf.m

changeset 10289: 4b124317dc38
parent:f0c3d3fc4903
author: John W. Eaton <jwe@octave.org>
date: Tue Feb 09 20:58:55 2010 -0500 (45 minutes ago)
permissions: -rw-r--r--
description: base_properties::set_children: account for hidden children 
     1## Copyright (C) 1995, 1996, 1997, 2006, 2007, 2009 Kurt Hornik

     2##

     3## This file is part of Octave.

     4##

     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.

     9##

    10## Octave is distributed in the hope that it will be useful, but

    11## WITHOUT ANY WARRANTY; without even the implied warranty of

    12## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

    13## General Public License for more details.

    14##

    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/>.

    18

    19## -*- texinfo -*-

    20## @deftypefn {Function File} {} wblcdf (@var{x}, @var{scale}, @var{shape})

    21## Compute the cumulative distribution function (CDF) at @var{x} of the

    22## Weibull distribution with shape parameter @var{scale} and scale

    23## parameter @var{shape}, which is

    24##

    25## @tex

    26## $$ 1 - \exp(-(x/shape)^{scale}) $$

    27## for $x\geq 0$.

    28## @end tex

    29## @ifnottex

    30## @example

    31## 1 - exp(-(x/shape)^scale)

    32## @end example

    33## for @var{x} >= 0.

    34## @end ifnottex

    35## @end deftypefn

    36

    37## Author: KH <Kurt.Hornik@wu-wien.ac.at>

    38## Description: CDF of the Weibull distribution

    39

    40function cdf = wblcdf (x, scale, shape)

    41

    42  if (nargin < 1 || nargin > 3)

    43    print_usage ();

    44  endif

    45

    46  if (nargin < 3)

    47    shape = 1;

    48  endif

    49

    50  if (nargin < 2)

    51    scale = 1;

    52  endif

    53

    54  if (!isscalar (shape) || !isscalar (scale))

    55    [retval, x, shape, scale] = common_size (x, shape, scale);

    56    if (retval > 0)

    57      error ("wblcdf: x, scale and shape must be of common size or scalar");

    58    endif

    59  endif

    60

    61  cdf = NaN * ones (size (x));

    62

    63  ok = ((shape > 0) & (shape < Inf) & (scale > 0) & (scale < Inf));

    64

    65  k = find ((x <= 0) & ok);

    66  if (any (k))

    67    cdf(k) = 0;

    68  endif

    69

    70  k = find ((x > 0) & (x < Inf) & ok);

    71  if (any (k))

    72    if (isscalar (shape) && isscalar (scale))

    73      cdf(k) = 1 - exp (- (x(k) / scale) .^ shape);

    74    else

    75      cdf(k) = 1 - exp (- (x(k) ./ scale(k)) .^ shape(k));

    76    endif

    77  endif

    78

    79  k = find ((x == Inf) & ok);

    80  if (any (k))

    81    cdf(k) = 1;

    82  endif

    83

    84endfunction