in reply to Re: random number generation.
in thread random number generation.

Thanks guys for your replies.

Hi Ikegami, how would your "rerolling duplicates" method work if the l
+ist just thrice (not long enough) the total numbers to be drawn. I gu
+ess "shuffle" would be a better alternative then?

Thanks.

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Re^3: random number generation.
by ikegami (Patriarch) on Sep 11, 2007 at 18:20 UTC
    The shorter the list, the more rerolls would have to be done. shuffle will work quite well in most settings even with hundreds of items.
[reply]
[d/l]
      Thank you very much Ikegami.

One last thing, if I want to create 3 sets of 5 integers each from the
+ integer range 1 to 15 then which one is better from randomness angle
+:

1. I shuffle the previously "shuffled" list in each iteration, or
2. I shuffle the "original" list in each iteration.

Here is the code:

Method 1:
my @array=(1..15);
my @shufflednumbers=();

foreach my $i (1..3) {
    @shufflednumbers = shuffle (@array);
    print "@shufflednumbers[0..4]";
    @shufflednumbers=();
}

Method 2:
my @array=(1..15);
my @temp=@array;
my @shufflednumbers=();

foreach my $i (1..3) {
    @shufflednumbers = shuffle (@temp);
    print "@shufflednumbers[0..4]";
    @temp=@shufflednumbers;
    @shufflednumbers=();
}

      [download]
[reply]
[d/l]
        Method 1 is fine. 
        my @array = (1..15);

for (1..3) {
    my @shufflednumbers = (shuffle(@array))[0..4];
    print "@shufflednumbers\n";
}

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[reply]
[d/l]

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