Return a random element from the array.
[1, 2, 3, 4].at_rand #~> 2 [1, 2, 3, 4].at_rand #~> 4
# File lib/standard/facets/random.rb, line 128 def at_rand at(Random.number(size)) end
Same as at_rand, but acts in place removing a random element from the array.
a = [1,2,3,4] a.at_rand! #~> 2 a #~> [1,3,4]
# File lib/standard/facets/random.rb, line 139 def at_rand! return delete_at( Random.number( size ) ) end
Similar to at_rand, but will return an array of randomly picked exclusive elements if given a number.
# File lib/standard/facets/random.rb, line 145 def pick(n=nil) if n a = self.dup a.pick!(n) else at(Random.number(size)) end end
Similar to at_rand!, but given a number will return an array of exclusive elements.
# File lib/standard/facets/random.rb, line 156 def pick!(n=nil) if n if n > self.size r = self.dup self.replace([]) r else r = [] n.times { r << delete_at(Random.number(size)) } r end else delete_at(Random.number(size)) end end
Random index.
# File lib/standard/facets/random.rb, line 174 def rand_index Random.number(size) end
Returns a random subset of an Array. If a number of elements is specified then returns that number of elements, otherwise returns a random number of elements upto the size of the Array.
By defualt the returned values are exclusive of each other, but if exclusive is set to false, the same values can be choosen more than once.
When exclusive is true (the default) and the number given is greater than the size of the array, then all values are returned.
[1, 2, 3, 4].rand_subset(1) #~> [2] [1, 2, 3, 4].rand_subset(4) #~> [2, 1, 3, 4] [1, 2, 3, 4].rand_subset #~> [1, 3, 4] [1, 2, 3, 4].rand_subset #~> [2, 3]
# File lib/standard/facets/random.rb, line 196 def rand_subset( number=nil, exclusive=true ) number = Random.number(size) unless number number = number.to_int #return self.dup if (number >= size and exlusive) return sort_by{rand}.slice(0,number) if exclusive ri =[]; number.times { |n| ri << Random.number(size) } return values_at(*ri) end
Randomize the order of an array.
[1,2,3,4].shuffle #~> [2,4,1,3]
# File lib/standard/facets/random.rb, line 209 def shuffle dup.shuffle! #sort_by{Random.number} end
As with shuffle but modifies the array in place. The algorithm used here is known as a Fisher-Yates shuffle.
a = [1,2,3,4] a.shuffle! a #~> [2,4,1,3]
CREDIT Niel Spring
# File lib/standard/facets/random.rb, line 223 def shuffle! s = size each_index do |j| i = Random.number(s-j) #self[j], self[j+i] = self[j+i], self[j] tmp = self[j] self[j] = self[j+i] self[j+i] = tmp end self end
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