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RandomSample

RandomSample[{e₁, e₂, ...}, n]
gives a pseudorandom sample of

of the

RandomSample[{w₁, w₂, ...}->{e₁, e₂, ...}, n]
gives a pseudorandom sample of

of the

chosen using weights

RandomSample[{e₁, e₂, ...}]
gives a pseudorandom permutation of the

RandomSample gives a different sequence of pseudorandom choices whenever you run Mathematica. You can start with a particular seed using SeedRandom.

A Method option to SeedRandom can be given to specify the pseudorandom generator used.

Find a sample in which no elements ever occur more than once:

Generate a random permutation:

Find a sample in which no elements ever occur more than once:

Generate a random permutation:

The elements can be any expressions:

With larger weights for later elements, later elements tend to be selected for the sample:

Successively fill in black squares down the page:

Use SeedRandom to get repeatable random values:

Use BlockRandom to block one use of RandomSample from affecting others:

RandomSample of size 1 follows the same distribution as RandomChoice:

If the sample size is larger than the population size an error message is returned: