SAS Procedures

Help using Base SAS procedures
BookmarkSubscribeRSS Feed
🔒 This topic is solved and locked. Need further help from the community? Please sign in and ask a new question.
peer
Calcite | Level 5

proc freq data=x nlevels;

table patient_id;

run;

I am trying to count the # of unique patients in this data.

Does the resulting output show the number of unique patient ids? or just the total amount of observations with non-missing ids.

Thank you, I appreciate the help.

1 ACCEPTED SOLUTION

Accepted Solutions
ballardw
Super User

If you need count of unique IDS:

proc sql:

     select count(*)

     from (select DISTINCT patient_id from x);

quit;

If you need list of unique ids:

proc sql;

     select distinct Patient_id

     from x;

quit;

View solution in original post

5 REPLIES 5
stat_sas
Ammonite | Level 13

It will provide total number of observations for each level of patient_id. So if each patient_id has one frequency then we can conclude that patient_id is unique.

Reeza
Super User

Not quite, NLEVELS does produce the number of distinct observations in the number of levels table.

Be careful of how it treats missing and how you want missing values treated though.

proc freq data=sashelp.class nlevels;

table age;

run;

ballardw
Super User

If you need count of unique IDS:

proc sql:

     select count(*)

     from (select DISTINCT patient_id from x);

quit;

If you need list of unique ids:

proc sql;

     select distinct Patient_id

     from x;

quit;

AaronDavid
Calcite | Level 5

To answer your question OP, the nlevels option will count distinct values, including missing values. The following code can help you break down multiple variables into unique values missing and non-missings much easier than performing the same task with a proc sql:

 

ods output nlevels=LEVELS;
proc freq data=dataset nlevels;
tables var1 var2 var3 var4 / noprint ;
run;
proc print data=LEVELS;
run;

sas-innovate-wordmark-2025-midnight.png

Register Today!

Join us for SAS Innovate 2025, our biggest and most exciting global event of the year, in Orlando, FL, from May 6-9. Sign up by March 14 for just $795.


Register now!

What is Bayesian Analysis?

Learn the difference between classical and Bayesian statistical approaches and see a few PROC examples to perform Bayesian analysis in this video.

Find more tutorials on the SAS Users YouTube channel.

SAS Training: Just a Click Away

 Ready to level-up your skills? Choose your own adventure.

Browse our catalog!

Discussion stats
  • 5 replies
  • 21713 views
  • 7 likes
  • 5 in conversation