Steffen Müller > Math-Random-AcceptReject-0.02 > Math::Random::AcceptReject

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Module Version: 0.02   Source  

NAME ^

Math::Random::AcceptReject - Acceptance-Rejection PDF transformations

SYNOPSIS ^

  use Math::Random::AcceptReject;
  my $pdf = Math::Random::AcceptReject->new(
    xmin   => 0, # defaults to 0
    xmax   => 2, # defaults to 1
    ymax   => 2, # no default!
    pdf    => 'x',    # a triangle from x=0 to x=2 with slope 1
    random => 'rand', # use Perl's builtin (default)
  );
  
  foreach (1..100) {
      my $rnd = $pdf->rand();
      # ...
  }
  
  # Use Math::Random::MT instead of bultin rand()
  # Same target PDF but as Perl code instead of a Math::Symbolic
  # function!
  use Math::Random::MT;
  my $mt = Math::Random::Mt->new($seed);
  $pdf = Math::Random::AcceptReject->new(
    xmax   => 2,
    ymax   => 2,
    pdf    => sub { $_[0] },
    random => sub { $mt->rand() };
  );

DESCRIPTION ^

This module implements acceptance-rejection transformations of uniformly distributed random numbers to mostly arbitrary probability density functions (PDFs).

Note that whereas J. von Neumann's algorithm can transform from arbitrary source PDFs to arbitrary destination PDFs, this module is currently limited to uniform [0,1] source PDFs!

METHODS ^

new

Creates a new random number generator. Takes named arguments.

Mandatory parameters:

  pdf:  The probability density function. This can either be a
        subroutine reference which takes an argument ('x') and
        returns f(x), a Math::Symbolic tree representing f(x) and
        using the variable 'x', or a string which can be parsed
        as such a Math::Symbolic tree.
  ymax: Maximum value of the target PDF f(x) in the x range. This
        max theoretically be safely set to a very large value which
        is much higher than the real maximum of f(x) within
        the range [xmin,xmax]. The efficiency of the algorithm goes
        down with 

Optional parameters:

  random: The random number generator. Defaults to using Perl's
          rand() function. May be set to either 'rand' for the
          default or a subroutine reference for custom random
          number generators. Expected to return one or more(!)
          random numbers per call.
  xmin:   Minimum value for x. Defaults to 0.
  xmax:   Maximum value for x. Defaults to 1.

rand

Returns the next random number of PDF f(x) as specified by the pdf parameter to new().

SEE ALSO ^

http://en.wikipedia.org/wiki/Rejection_sampling

Math::Random::MT, Math::Random, Math::Random::OO, Math::TrulyRandom

Math::Symbolic

The examples in the examples/ subdirectory of this distribution.

AUTHOR ^

Steffen Mueller, <smueller@cpan.org>

COPYRIGHT AND LICENSE ^

Copyright (C) 2007 by Steffen Mueller

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself, either Perl version 5.6 or, at your option, any later version of Perl 5 you may have available.

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