topic Re: Random selection of 1 from 2 in SAS Programming

Random selection of 1 from 2

Miracle — Wed, 28 Oct 2020 16:38:07 GMT

Dear All,
I have one question on random selection of 1 from 2.
Let say a person has 2 eyes and we randomly select only one eye i.e. either left or right.
Are we actually able to get the same eye for everyone every time we run our program?

Apologies that it's not SAS-related.

Re: Random selection of 1 from 2

FreelanceReinh — Wed, 28 Oct 2020 17:28:42 GMT

Hello @Miracle,

It depends on whether you specify a positive random seed.

Example:

data want;
call streaminit(27182818);
set sashelp.class;
length random_eye $5;
random_eye=choosec(rand('table',0.5),'left','right');
run;

Thanks to the CALL STREAMINIT statement with a positive argument, the 19 assignments to variable random_eye will be the same every time you run the program. Change the argument to a different positive value (e.g., 1) and you'll get (in general) a different, but again stable set of assignments. Without the CALL STREAMINIT statement or using 0 as its argument the assignments will (in general) change from run to run.

Re: Random selection of 1 from 2

PGStats — Wed, 28 Oct 2020 17:33:13 GMT

SAS provides pseudo-random number generating functions. These functions can be set to start the random number sequence at a given point, determined by a seed value. For example the program

data eyes;
call streaminit(852559); /* Set the random number generation seed */
set sashelp.class;
selectedEye = rand("integer", 2); /* Generate a random number */
run;

proc print; run;

should give you this same pseudo-random sequence :

Re: Random selection of 1 from 2

ballardw — Wed, 28 Oct 2020 22:10:06 GMT

If I recall correctly, the ability to duplicate the random number stream is somewhat software and hardware dependent. If you run the code on a different version of SAS, or on a machine with a different math co-processor the results may differ.

Re: Random selection of 1 from 2

Ksharp — Thu, 29 Oct 2020 12:25:55 GMT

Calling @Rick_SAS

Re: Random selection of 1 from 2

Miracle — Thu, 29 Oct 2020 13:17:14 GMT

Thank you all for your response @FreelanceReinh, @PGStats, @ballardw and @Ksharp.
I have used the call streaminit and it gives me the same eye all the time.