Random assignment operators

PlanOut comes built in with several built-in random assignment operators that map units to randomized values. All operators require one to specify an input unit, and optionally allow one to specify a salt. For more details on how randomization works, see the how PlanOut works page.


UniformChoice takes an argument choices and selects among these choices with uniform probability.

params.x = UniformChoice(choices=['a', 'b'], unit=userid)
params.y = UniformChoice(choices=['a', 'b', 'c'], unit=userid)

In the code above, x will take on the values ‘a’ and ‘b’ a 1/2 probability each, and y will take on the values ‘a’, ‘b’, and ‘c’ with a 1/3 probability each.


WeightedChoice selects among multiple choices (choices) with a given set of weights (weights).

params.x = WeightedChoice(choices=['a', 'b', 'c'], weights=[0.8, 0.1, 0.1],
params.y = WeightedChoice(choices=['a', 'b', 'c'], weights=[8, 1, 1],

Both x and y will take on the values ‘a’, ‘b’, and ‘c’ with a 80%, 10%, and 10% chance each. Because x and y have different salts, they will not necessarily always have the same values for a given userid.


WeightedChoice flips a coin that lands on 1 with probability p, and 0 with probability 1-p.

params.x = BernoulliTrial(p=0.0, unit=userid)
params.y = BernoulliTrial(p=0.2, unit=userid)

In the code above, x will always be 0, and y will be 1 20% of the time.


RandomFloat generates a random floating point number between min and max.

params.x = RandomFloat(min=0.0, max=10.0), unit=userid)


RandomInteger generates a random integer between min and max, inclusive.

params.x = RandomFloat(min=0, max=10), unit=userid)


Sample samples from a list without replacement. It has one required parameter, choices, and an optional parameter, num_draws. If num_draws is not specified, then Sample will simply shuffle the input array.

params.x = Sample(choices=['a','b','c'])
params.y = Sample(choices=['a','b','c'], num_draws=2)

In the code above, x will be a three element list, containing ‘a’, ‘b’, and ‘c’, exactly once, in a random order, and y be a two-element subset of ['a','b', 'c'].