RANPOI Function

Returns a random variate from a Poisson distribution

Category: Random Number

Tip: If you want to change the seed value during execution, you must use the CALL RANPOI routine instead of the RANPOI function.

Syntax

RANPOI ( seed,m )

Arguments

seed

• is an integer. If seed ‰ 0, the time of day is used to initialize the seed stream.

• Range: seed < 2 ³¹ -1

• See: 'Seed Values' on page 257 for more information about seed values

m

• is a numeric mean parameter.

• Range: m ‰

Details

The RANPOI function returns a variate that is generated from a Poisson distribution with mean m . For m < 85, an inverse transform method applied to a RANUNI uniform variate is used (Fishman 1976) (See 'References' on page 926). For m ‰ 85, the normal approximation of a Poisson random variable is used. To expedite execution, internal variables are calculated only on initial calls (that is, with each new m ).

Comparisons

The CALL RANPOI routine, an alternative to the RANPOI function, gives greater control of the seed and random number streams.

See Also

Call routine:

'CALL RANPOI Routine' on page 377