From: James Edward Gray II <james@...>
Date: 2007-02-26T01:41:58+09:00
Subject: Re: extract a random number of items from an array

On Feb 25, 2007, at 10:20 AM, Josselin wrote:

> given an array of values, how should I extract an random number of  
> these values
>
> a = [13, 15, 17, 18, 19, 20, 21, 23, 24, 25, 26, 27, 28, 29, 30,  
> 31, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56,  
> 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73,  
> 74, 75, 76, 77, 78, 79, 81, 82, 83, 84, 85, 86, 88, 89, 90, 91, 92,  
> 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106]

Just give a random chance that a value is added to the result set:

 >> a.select { rand(2).zero? }
=> [13, 15, 23, 24, 25, 26, 27, 28, 29, 31, 41, 42, 44, 45, 46, 47,  
49, 51, 52, 53, 55, 58, 60, 61, 62, 66, 67, 68, 69, 70, 71, 72, 73,  
75, 76, 78, 81, 82, 83, 89, 90, 91, 94, 95, 98, 99, 100, 101, 103,  
104, 105, 106]
 >> a.select { rand(2).zero? }
=> [13, 18, 19, 20, 21, 24, 26, 27, 28, 29, 30, 31, 41, 42, 44, 48,  
49, 51, 52, 53, 55, 57, 58, 59, 62, 63, 64, 66, 68, 70, 79, 81, 82,  
83, 86, 89, 90, 91, 92, 94, 97, 98, 102, 104, 105, 106]
 >> a.select { rand(2).zero? }
=> [15, 17, 18, 19, 20, 21, 23, 25, 30, 41, 44, 45, 46, 49, 50, 51,  
52, 53, 54, 57, 59, 63, 64, 66, 68, 70, 72, 73, 76, 78, 79, 81, 82,  
90, 91, 95, 97, 101, 102, 104]

Hope that helps.

James Edward Gray II