Re: simple probability problem using PERL

[James Edward Gray II]

On Jan 24, 2004, at 5:31 PM, Charles Lu wrote:

Hi

 If I want to randomly generate a dice (4 side) roll, I can use the 
following expression:

   $roll = 1 + int( rand(4));

This assumes that every side of this dice has equal chance of being 
rolled (0.25).  Thats easy.  Now What if I say, that the probability 
of rolling a 3 is 70% and the probability of rolling a 1 or 2 or 4 is 
10%.

i.e.
$probability = {  '1' => 0.1,
                      '2' => 0.1,
                      '3' => 0.7,
                      '4 => 0.1
                    }
Notice the total probability still addes up to 1.  So If I want to 
roll this "loaded" dice, how should I modify the above code to 
accurately reflect the different weight of this new dice?  Any 
suggestion would be appreciated.  Thanks.
How about something like this:

sub roll_loaded_die {
        my $roll = rand;
        if ($roll <= .1) { return 1; }
        elsif ($roll <= .2) { return 2; }
        elsif ($roll <= .3) { return 4; }
        else { return 3; }
}
Hope that helps.

James

--
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
<http://learn.perl.org/> <http://learn.perl.org/first-response>