class Hash

internal method to validate parameters

# File lib/hash_sample.rb, line 52
def _check_weighted_params(*_args)
  sum_weights = 0
  each_value do |v|
    raise ArgumentError, "All weights should be numeric unlike #{v}" unless v.is_a? Numeric

    sum_weights += v if v.positive?
  end

  raise ArgumentError, "At least one weight should be > 0" unless sum_weights.positive? || empty?
end

Choose a random key=>value pair or n random pairs from the hash.

@return [Hash] new Hash containing sample key=>value pairs

The elements are chosen by using random and unique indices in order to ensure that each element doesn't includes more than once. If the hash is empty it returns an empty hash. If the hash contains less than n unique keys, the copy of whole hash will be returned, none of keys will be lost.

# File lib/hash_sample.rb, line 11
def sample(n = 1)
  to_a.sample(n).to_h
end

Choose 1 or n random keys from the hash, according to weights defined in hash values (weighted random sampling with replacement)

@overload wchoice

@return [Object] one sample object

@overload wchoice(n)

@param n [Integer] number of samples to be returned
@return [Array] Array of n samples

The keys are chosen by using random according to its weights and can be repeated in result. If the hash is empty the first form returns nil and the second form returns an empty array. All weights should be Numeric. Zero or negative weighs will be ignored.

Example¶ ↑

p {'_' => 9, 'a' => 1}.wchoice(10)  # ["_", "a", "_", "_", "_", "_", "_", "_", "_", "_"]

# File lib/hash_sample.rb, line 40
def wchoice(*args)
  _check_weighted_params
  n = args.first || 1
  res = []
  n.times do
    tmp = max_by { |_, weight| weight.positive? ? rand**(1.0 / weight) : 0 }
    res << tmp.first unless tmp.nil?
  end
  return args.empty? ? res.first : res
end

alias for wchoice

# File lib/hash_sample.rb, line 17
def wchoices(*args)
  wchoice(*args)
end

Choose 1 or n distinct random keys from the hash, according to weights defined in hash values (weighted random sampling without replacement)

@overload wsample

@return [Object] one sample object

@overload wsample(n)

@param n [Integer] number of samples to be returned
@return [Array] Array of n or sometimes less than n samples

When there are no sufficient distinct samples to return, the result will contain less than n samples If the hash is empty the first form returns nil and the second form returns an empty array. All weights should be Numeric. Zero or negative weighs will be ignored.

Example¶ ↑

p {'_' => 9, 'a' => 1}.wsample(10)  # ["_", "a"]

# File lib/hash_sample.rb, line 82
def wsample(*args)
  _check_weighted_params
  n = args.first || 1
  res = max_by(n) { |_, weight| weight.positive? ? rand**(1.0 / weight) : 0 }.map(&:first)
  return args.empty? ? res.first : res
end

alias for wsample

# File lib/hash_sample.rb, line 91
def wsamples(*args)
  wsample(*args)
end