Re: random elements with fixed totals

I think this is in Knuth, but I'm too lazy to look it up. Assuming that $N and $M are set:

my @a = map {my $e = rand $N -- < $M; $e && $M --; $e || 0} 1 .. $N;
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Abigail

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Re: Re: random elements with fixed totals by ysth (Canon) on Nov 16, 2003 at 07:21 UTC
I looked in Knuth before asking and didn't see it. But that is just the algorithm I am worried will distort the distribution at the end! For instance, if M is one, the probability of the first element being set is 1/N, but the probability of the last element being set is ... (N-1)!/N! Oh. (Whacks self on head.) Knuth 3.4.2 Random Sampling and Shuffling, Algorithm S Thanks, Abigail	[reply]