how to count the number of subjects in a recode

[hjjijkkl]

How do you count the number of subjects in a big dataset? Each subject has serval records , is there a way to find the number of subjects in the dataset?

[PhilC · Accepted solution]

Take for instance the example data set SASHELP.SHOES.  Imagine that the region column identifies your subjects.  Then...

PROC SQL;
   SELECT COUNT(DISTINCT(Region))) AS COUNT_DISTINCT_of_Region
      FROM SASHELP.SHOES ;
QUIT;

We find with this that there are 10 regions (or imagined subjects). 

Related article: Your data ain't good looking, but it has a nice cardinality - The SAS Dummy

[Reeza]

Define big.

If you get really, really big, you may want a hash solution. Otherwise, here are two ways to find the distinct counts;
https://github.com/statgeek/SAS-Tutorials/blob/master/count_distinct_by_group.sas