Functions and CALL Routines

CALL RANUNI Routine

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. A new value for seed is returned each time CALL RANUNI is executed.

Range:	seed < 2³¹ - 1
Tip:	If seed 0, the time of day is used to initialize the seed stream.
See:	Seed Values and Comparison of Seed Values in Random-Number Functions and CALL Routines for more information about seed values

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.

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 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 pageno=1 nodate ls=80 ps=64;

data u1(keep=x);
   seed = 104;
   do i = 1 to 5;
      call ranuni(seed, x);
      output;
   end;
   call symputx('seed', seed);
run;

data u2(keep=x);
   seed = &seed;
   do i = 1 to 5;
      call ranuni(seed, x);
      output;
   end;
run;

data all;
   set u1 u2;
   z = ranuni(104);
run;

proc print label;
   label x = 'Separate Streams' z = 'Single Stream';
run;

The following output shows the results:

Output from the CALL RANUNI Routine

                                 The SAS System                                1

                                  Separate     Single
                           Obs     Streams     Stream

                             1     0.23611    0.23611
                             2     0.88923    0.88923
                             3     0.58173    0.58173
                             4     0.97746    0.97746
                             5     0.84667    0.84667
                             6     0.80484    0.80484
                             7     0.46983    0.46983
                             8     0.29594    0.29594
                             9     0.17858    0.17858
                            10     0.92292    0.92292