如何从SAS数据集中输出随机观察值

Question

I have a data set that selects random numbers from a uniform distribution. How do you only output those row indices? I basically want to select a random set of rows from a SAS data set.

data Unif(keep=u x k n m);
call streaminit(123);
a = -1; b = 1;
Min = 1; Max = 28000000;
do i = 1 to &NObs;
   u = rand("Uniform");    /* U[0,1] */
   x = a + (b-a)*u;        /* U[a,b] */
   k = ceil( Max*u );      /* uniform integer in 1..Max */
   n = floor( (1+Max)*u ); /* uniform integer in 0..Max */
   m = min + floor((1+Max-Min)*u); /* uniform integer in Min..Max */
   output;
end;
keep k
run;
     *not sure about this part;
    data final;
     set final;
     where obs in (k);
   run;

Answer 1

The best way to do this is to use PROC SURVEYSELECT .

proc surveyselect data=final out=selected seed=123 n=10;
run;

Or something along those lines depending on how you want to run it - the documentation has a lot of detail on the various options for how to perform the sampling.

If you want to do it in the datastep, you need to be running the code from Unif inside the second datastep, in some fashion. I don't entirely follow what it's trying to do; if that's a form of k/n sampling, search 'SAS k/n sampling' and you'll find lots out there as it's a common question, but the general approach is

data final_selected;
set final;
... code to determine if it should be selected...
if (condition); *subsetting if;
run;