Re: Random number generator
On 4/9/09 Thu Apr 9, 2009 2:34 PM, ANJAN PURKAYASTHA
anjan.purkayas...@gmail.com scribbled:
I need a Bernoulli random number generator which takes as inputs: a value
for p(1) (probability of choosing a 1) and the number of trials and
outputs a series of 0s and 1s according to the model B(p(1)).
Any thoughts on which module I need to use?
I am not sure what a Bernoulli random number generator is, but I am guessing
it is an algorithm that generates values 0 or 1 based on a probability of
picking a 1. If that is not correct, ignore the following (:^).
Do you need a module? It would seem easy enough to generate an array of
true/false values:
sub bernoulli
{
my( $p, $n ) = @_;
return map { (rand() $p) } (1..$n);
}
or explicit 0s and 1s:
sub bernoulli
{
my( $p, $n ) = @_;
return map { (rand() $p) ? 1 : 0 } (1..$n);
}
or you can just return a 0 or 1 on each call:
sub bernoulli
{
my( $p, $n ) = @_;
return (rand() $p) ? 1 : 0;
}
(but then you don't need to pass the routine the number of trials).
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Re: Random number generator
On Thu, Apr 9, 2009 at 17:34, ANJAN PURKAYASTHA anjan.purkayas...@gmail.com wrote: I need a Bernoulli random number generator which takes as inputs: a value for p(1) (probability of choosing a 1) and the number of trials and outputs a series of 0s and 1s according to the model B(p(1)). Any thoughts on which module I need to use? snip When you need something the first place to look is CPAN[1]. The Math::GSL[2] module has a function sounds like it fits your needs: gsl_ran_bernoulli($r, $p) - This function returns either 0 or 1, the result of a Bernoulli trial with probability $p. The probability distribution for a Bernoulli trial is, p(0) = 1 - $p and p(1) = $p. $r is a gsl_rng structure. gsl_ran_bernoulli_pdf($k, $p) - This function computes the probability p($k) of obtaining $k from a Bernoulli distribution with probability parameter $p, using the formula given above. 1. http://search.cpan.org/ 2. http://search.cpan.org/dist/Math-GSL/lib/Math/GSL/Randist.pm -- Chas. Owens wonkden.net The most important skill a programmer can have is the ability to read. -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
Re: Random number generator
Thank you guys. Anjan On Thu, Apr 9, 2009 at 6:59 PM, Chas. Owens chas.ow...@gmail.com wrote: On Thu, Apr 9, 2009 at 17:34, ANJAN PURKAYASTHA anjan.purkayas...@gmail.com wrote: I need a Bernoulli random number generator which takes as inputs: a value for p(1) (probability of choosing a 1) and the number of trials and outputs a series of 0s and 1s according to the model B(p(1)). Any thoughts on which module I need to use? snip When you need something the first place to look is CPAN[1]. The Math::GSL[2] module has a function sounds like it fits your needs: gsl_ran_bernoulli($r, $p) - This function returns either 0 or 1, the result of a Bernoulli trial with probability $p. The probability distribution for a Bernoulli trial is, p(0) = 1 - $p and p(1) = $p. $r is a gsl_rng structure. gsl_ran_bernoulli_pdf($k, $p) - This function computes the probability p($k) of obtaining $k from a Bernoulli distribution with probability parameter $p, using the formula given above. 1. http://search.cpan.org/ 2. http://search.cpan.org/dist/Math-GSL/lib/Math/GSL/Randist.pm -- Chas. Owens wonkden.net The most important skill a programmer can have is the ability to read. -- = anjan purkayastha, phd bioinformatics analyst whitehead institute for biomedical research nine cambridge center cambridge, ma 02142 purkayas [at] wi [dot] mit [dot] edu 703.740.6939
