Functions and CALL Routines 
Category:  Random Number 
Syntax  
Arguments  
Details  
Comparisons  
Examples  
See Also 
Syntax 
CALL RANPOI(seed,m,x); 
is the seed value. A new value for seed is returned each time CALL RANPOI is executed.
Range:  seed < 2^{31}  1 
Note:  If seed 0, the time of day is used to initialize the seed stream. 
See:  Seed Values and Comparison of Seed Values in RandomNumber Functions and CALL Routines for more information about seed values 
Range:  m 0 
is a numeric variable. A new value for the random variate x is returned each time CALL RANPOI is executed.
Details 
The CALL RANPOI routine updates seed and returns a variate x that is generated from a Poisson distribution, with mean m.
By adjusting the seeds, you can force streams of variates to agree or disagree for some or all of the observations in the same, or in subsequent, DATA steps.
For m< 85, an inverse transform method applied to a RANUNI uniform variate is used (Fishman, 1976; see in References). 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).
For a discussion and example of an effective use of the random number CALL routines, see Starting, Stopping, and Restarting a Stream.
Comparisons 
The CALL RANPOI routine gives greater control of the seed and random number streams than does the RANPOI function.
Examples 
This example uses the CALL RANPOI routine:
options pageno=1 ls=80 ps=64 nodate; data u1(keep=x); seed = 104; do i = 1 to 5; call ranpoi(seed, 2000, x); output; end; call symputx('seed', seed); run; data u2(keep=x); seed = &seed; do i = 1 to 5; call ranpoi(seed, 2000, x); output; end; run; data all; set u1 u2; z = ranpoi(104, 2000); run; proc print label; label x = 'Separate Streams' z = 'Single Stream'; run;
Output from the CALL RANPOI Routine
The SAS System 1 Separate Single Obs Streams Stream 1 2058 2058 2 2046 2046 3 2009 2009 4 1984 1984 5 2073 2073 6 1921 1921 7 2034 2034 8 2042 2042 9 2001 2001 10 1957 1957
See Also 

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