CALL RANTRI Routine

Returns a random variate from a triangular distribution

Category: Random Number

Syntax

CALL RANTRI ( seed,h,x );

Arguments

seed

• is the seed value. A new value for seed is returned each time CALL RANTRI 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

h

• is a numeric SAS value.

• Range: 0 < h < 1

x

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

Details

The CALL RANTRI routine updates seed and returns a variate x generated from a triangular distribution on the interval (0,1) with parameter h , which is the modal value of the distribution.

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.

The CALL RANTRI routine uses an inverse transform method applied to a RANUNI uniform variate.

Comparisons

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

Examples

This example uses the CALL RANTRI routine:

 options nodate pageno=1 linesize=80 pagesize=60;  data case;     retain Seed_1 Seed_2 Seed_3 45;     h=.2;     do i=1 to 10;        call rantri(Seed_1,h,X1);        call rantri(Seed_2,h,X2);        X3=rantri(Seed_3,h);        if i=5 then           do;              Seed_2=18;              Seed_3=18;           end;        output;     end;  run;  proc print;     id i;     var Seed_1-Seed_3 X1-X3;  run; 

The following output shows the results:

Output 4.13: The RANTRI Example

 The SAS System                                    1    i      Seed_1             Seed_2    Seed_3        X1           X2             X3    1      694315054       694315054      45       0.26424       0.26424       0.26424    2     1404437564      1404437564      45       0.47388       0.47388       0.47388    3     2130505156      2130505156      45       0.92047       0.92047       0.92047    4     1445125588      1445125588      45       0.48848       0.48848       0.48848    5     1013861398              18      18       0.35015       0.35015       0.35015    6     1326029789       707222751      18       0.44681       0.26751       0.44681    7      932142747       991271755      18       0.32713       0.34371       0.32713    8     1988843719       422705333      18       0.75690       0.19841       0.75690    9      516966271      1437043694      18       0.22063       0.48555       0.22063   10      2137808851     1264538018      18       0.93997       0.42648       0.93997 

 

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

See Also

Function:

• 'RANTRI Function' on page 783