Stata Numeric Functions

Stata supports these numeric functions in the global scope.

Random Number Functions

Runiform

runiform(a,b) returns a random number between a and b. If no parameters are specified, the defaults of 0 and 1 are used.

Below is a demonstration for how an SRS sample can be drawn.

set seed 123456
generate double r_sampled = runiform()
sort r_sampled
generate byte sampled = _n <= 100 

The return value is a double; it will be within a + c(epsdouble) and b − c(epsdouble).

By default, runiform uses the 64-bit Mersenne Twister algorithm. Alternate algorithms are available; see set rng.

Set Rng

To use an alternate random number generation algorithm, set the rng value to something other than default.

set rng default

Possible values include...

• mt64 (64-bit Mersenne Twister)

• mt64s (stream algorithm based on the 64-bit Mersenne Twister)

• kiss32 (32-bit keep it simple stupid)

In Stata 14, the default flipped from kiss32 to mt64.

Set Seed

To make random number generation reproducible, set a seed value.

set seed 42

A seed value must be an integer, non-negative, and no greater than 2³¹ − 1.

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