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Answer: How do I get random numbers that follow standard distribution?

by sinan (Sexton)
on Aug 27, 2000 at 14:12 UTC ( #29883=categorized answer: print w/replies, xml ) Need Help??

Q&A > math > How do I get random numbers that follow standard distribution? - Answer contributed by sinan

I finally did something that solves the problem partially.

The two following functions do that. The first function, rands will return a "standard" randomized integer. It has two input values: The first input variables denote the range of the output. (i.e. 0 to input) The second one will denote the precision: Higher it is, closer the result will be to the normal distribution. 5 is more than enough for many purposes.

The second function (random) is a little bit more tricky. The first input is the range, just like in the first function. The second input is a string which can either be "low" or "high". The third input is a limit. If the second input is "low", then the third input denotes the lowest possible number. If it is high, then it denotes the highest possible number. All the results that are outside either the lowest or the highest frequency will be ignored and "re-rolled".

Here is the snippet:
sub rands{ my $t=0; $t = 0; $t+= ( rand()* ($_[0]/$_[1]) ) for(1..$_[1]); return int($t+1); } sub random{ my ($no,$type,$limit) = @_; $t = rands($no,5); if($type eq "low"){ while ($t<$limit){ $t = rands($no,5) } } elsif($type eq "high"){ while ($t>$limit){ $t = rands($no,5) } } }
I was not able to "skew" my results, so I used this _harsh_ method of cutting off instead.

One final note: You can set the second input variable of rands to a low number (2,3) to get a more homogenous distribution, i.e. a distribution with "high variance".

Sinan

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