CALL RANUNI

CALL RANUNI

Returns a random variate from a uniform distribution

Category: Random Number

Syntax
Arguments
Details
Comparisons
Examples
See Also

Syntax

CALL RANUNI(seed,x);

Arguments

seed

is the seed value. For more information about seeds, see Seed Values. A new value for seed is returned each time CALL RANUNI is executed.

Range:	*seed* < 2³¹ - 1
Note	If *seed* 0, the time of day is used to initialize the seed stream.

x

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

Details

The CALL RANUNI routine updates seed and returns a variate x that is generated from the uniform distribution on the interval (0,1), using a prime modulus multiplicative generator with modulus 2³¹-1 and multiplier 397204094 (Fishman and Moore 1982) (See References).

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.

Comparisons

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

Examples

This example uses the CALL RANUNI routine:

options nodate pageno=1 linesize=80 pagesize=60;  

data case;
   retain Seed_1 Seed_2 Seed_3 45;
   do i=1 to 10;
      call ranuni(Seed_1,X1);
      call ranuni(Seed_2,X2);
      X3=ranuni(Seed_3);
      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 RANUNI Example shows the results.

The RANUNI Example

The SAS System 1 i Seed_1 Seed_2 Seed_3 X1 X2 X3 1 694315054 694315054 45 0.32332 0.32332 0.32332 2 1404437564 1404437564 45 0.65399 0.65399 0.65399 3 2130505156 2130505156 45 0.99209 0.99209 0.99209 4 1445125588 1445125588 45 0.67294 0.67294 0.67294 5 1013861398 18 18 0.47212 0.47212 0.47212 6 1326029789 707222751 18 0.61748 0.32933 0.61748 7 932142747 991271755 18 0.43406 0.46160 0.43406 8 1988843719 422705333 18 0.92613 0.19684 0.92613 9 516966271 1437043694 18 0.24073 0.66918 0.24073 10 2137808851 1264538018 18 0.99549 0.58885 0.99549

Changing Seed_2 for the CALL RANUNI 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 RANUNI function, however, has no effect.

See Also

Function:

RANUNI

Chapter Contents
Previous
Next
Top of Page