sample_with_replacement¶
Syntax¶
sample_with_replacement(list-expression, expression)
sample_with_replacement(list-expression, expression, weight-list-expression)
Parameters¶
list-expression- An expression that evaluates to the list to select from.
expression- An expression that evaluates to the number of samples to return
weight-list-expression- An expression that evaluates to the list of weights to be used in the sampling.
Returns¶
The action returns a list. The returned list is empty if the first argument evaluates to an empty list or if the second argument evaluates to 0.
Description¶
This action returns a list of values randomly sampled from the first argument with replacement. The number of samples is specified by the second argument. Each call to the action returns a distinct random sample.
An optional, weight list can be specified in order to set a normalized
probability for the correspdonding index in the sample pool list being drawn.
For example, a weight list: list(1, 0, 1) will have a 50% chance that the
element with index 0, will be selected, a 50% chance that the element with
index 2 will be selected, and a 0% chance that the element with index 1 will be
selected.
Examples¶
Example of an un-weighted sampling:
x_list = list(1, 2, 3, 4, 5, 6, 7)
sample_list = sample_with_replacement(x_list, 4)
# possible result: sample_list = list(5, 2, 7, 2)
Example of a weighted sampling:
x_list = list(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)
weight_list = apply(x_list, pow(_, 2))
# weight_list = list(1, 4, 9, 16, 25, 36, 49, 64, 81, 100)
sample_list = sample_with_replacement(x_list, 4, weight_list)
# possible result: sample_list = list(10, 9, 7, 9)