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Generate from list

Generates a value from a given list

Evaluation

This expression evaluates to a function of the form:

(seed) -> any

The function is consistent with generator semantics of the Random Data step.

Processing

Given a seed value, the function returns an item pseudo-randomly selected from a list.

Settings

Name Type Description
Items
 list The list to pick a random item from.
Distribution
 any

Distribution of generated values.

Available options are:

  • uniform
    all possible values are generated with about the same probability
  • prefer start
    values at the start of the specified range are generated more frequently
  • prefer middle
    values in the middle of the specified range are generated more frequently
  • prefer end
    values at the end of the specified range are generated more frequently
  • strongly prefer start
    values at the start of the specified range are generated much more frequently
  • strongly prefer middle
    values in the middle of the specified range are generated much more frequently
  • strongly prefer end
    values at the end of the specified range are generated much more frequently
Custom Distribution Support

Alternatively, a list of double values between 0.0 and 1.0 is accepted.

The double value at each index corresponds to the same index in the item list and specifies the probability that the corresponding item is chosen from the list.

For example: an item list of ["Alice", "Bob", "Charlie"] and a distribution list of [0.5, 0.4, 0.1] makes the names appear with the given probabilities.

The following rules apply:

  • If the list of probabilities is shorter than the list of items, any remaining probability space is distributed equally among the remaining items.
  • If the list of probabilities is longer than the list of items, an error is thrown.
  • If the list of probabilities adds to less than 1.0 the difference corresponds to the probability of generating nil.
  • If the list of probabilities adds to more than 1.0 the behavior of the generator is undefined.
Chance of nil
 double Probability in range of 0.0 to 1.0 that the generator will return nil instead of generating a value.
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