RandomInt

RandomInt

RandomInt[ {min, max} ] randomly selects one or more integers from a range.

Usages

RandomInt[ {min, max} ]

RandomInt[ {min, max} ] returns a random integer from min to max, including min and max. Each time the exercise is generated, a new number is chosen, so the outputs below are only examples.

Example in out
A random integer from 1 to 5. RandomInt[ {1, 5} ] for example 4

RandomInt[ {min, max}, n ]

RandomInt[ {min, max}, n ] returns a list of n random integers from min to max. The list may contain the same number more than once; use the option AllowDuplicates to prevent this.

Example in out
3 random integers from 1 to 5. RandomInt[ {1, 5}, 3 ] for example {5, 3, 3}
The range and the number can be script variables. x := 3
y := 10
n := 2
r := RandomInt[{x, y}, n]		 for example r = {3, 7}
Options

AllowDuplicates

If set to False, every number is drawn at most once. Default: True.

Syntax Example out
RandomInt[ {min, max}, n, AllowDuplicates=>False ] RandomInt[ {1, 10}, 5, AllowDuplicates=>False ] for example {3, 4, 9, 10, 1}

Exclude

Numbers that must not be drawn. The value can be a single number or a list of numbers.

Syntax Example out
RandomInt[ {min, max}, Exclude=>{m1, m2, ...} ] RandomInt[ {-5, 5}, Exclude=>{0, 1} ] for example 4
RandomInt[ {min, max}, n, Exclude=>m ] RandomInt[ {-5, 5}, 4, Exclude=>0 ] for example {-1, 2, 3, 4}
Details
  • Order of the range: if min is larger than max, they are swapped: RandomInt[ {5, 1} ] works like RandomInt[ {1, 5} ].
  • Non-integer bounds are rounded inwards: RandomInt[ {1.5, 4.5} ] chooses from 2, 3 and 4.
  • Zero numbers: RandomInt[ {1, 5}, 0 ] returns {}.
  • Older notation: RandomInt[ min, max ], without the list, still works but should not be used in new scripts.
Invalid input Result
RandomInt[ {1, 5, 7} ] Error: the number range should have format {min, max}
RandomInt[ {1, x} ] Error: The minimum and maximum of the range must be numerical
RandomInt[ {1, 3}, 4, AllowDuplicates=>False ] Error: the given range contains fewer valid elements than the number requested
RandomInt[ {1, 5}, -1 ] Left unevaluated.
Warning
  • If Exclude removes every number in the range, such as RandomInt[ {1, 2}, Exclude=>{1, 2} ], the script stops with an internal error.
  • n should be an integer: RandomInt[ {1, 5}, 2.5 ] silently returns 2 numbers.
  • Unknown options are ignored without an error, so check the spelling of AllowDuplicates and Exclude.

See also: RandomSelect, RandomSample, Shuffle