CALL RANTBL Routine

Returns a random variate from a tabled probability distribution

Category: Random Number

Syntax

CALL RANTBL ( seed,p ₁ ,... p _i ,... p _n ,x );

Arguments

seed

• is the seed value. A new value for seed is returned each time CALL RANTBL 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' on page 257 for more information about seed values

p _i

• is a numeric SAS value.

• Range: ‰ p _i ‰ 1 for 0< i ‰ n

x

• is a numeric SAS variable. A new value for the random variate x is returned each time CALL RANTBL is executed.

Details

The CALL RANTBL routine updates seed and returns a variate x generated from the probability mass function defined by p ₁ through p _n .

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.

An inverse transform method applied to a RANUNI uniform variate is used. The CALL RANTBL routine returns these data:

If, for some index j < n ,

RANTBL returns only the indices 1 through j , with the probability of occurrence of the index j equal to

Comparisons

The CALL RANTBL routine gives greater control of the seed and random number streams than does the RANTBL function.

Examples

This example uses the CALL RANTBL routine:

 options nodate pageno=1 linesize=80 pagesize=60;  data case;     retain Seed_1 Seed_2 Seed_3 45;     input p1-p9;     do i=1 to 10;        call rantbl(Seed_1,of p1-p9,X1);        call rantbl(Seed_2,of p1-p9,X2);        X3=rantbl(Seed_3,of p1-p9);        if i=5 then           do;              Seed_2=18;              Seed_3=18;           end;        output;     end;     datalines;  .02 .04 .06 .08 .1 .12 .14 .16 .18  ;  proc print;     id i;     var Seed_1-Seed_3 X1-X3;  run; 

The following output shows the results:

Output 4.12: The RANTBL Example

 The SAS System                                     1    i       Seed_1            Seed_2    Seed_3     X1     X2     X3    1      694315054       694315054      45        6      6      6    2     1404437564      1404437564      45        8      8      8    3     2130505156      2130505156      45       10     10     10    4     1445125588      1445125588      45        8      8      8    5     1013861398              18      18        7      7      7    6     1326029789       707222751      18        8      6      8    7      932142747       991271755      18        7      7      7    8     1988843719       422705333      18       10      4     10    9      516966271      1437043694      18        5      8      5   10     2137808851      1264538018      18       10      8     10 

 

Changing Seed_2 for the CALL RANTBL statement, when I=5, forces the stream of variates for X2 to deviate from the stream of variates for X1. Changing Seed_3 on the RANTBL function, however, has no effect.

See Also

Function:

• 'RANTBL Function' on page 781