topic Re: Unusual result with FIRSTOBS and OBS option with WHERE statement in SAS Programming

Unusual result with FIRSTOBS and OBS option with WHERE statement

Nipun22 — Thu, 10 Oct 2024 13:22:27 GMT

Main code with problem

proc print data=SASHELP.CLASS(firstobs=5 obs=15);
where Sex='M';
run;

So the general meaning of the above program is that observations whose sex is 'Male' will starting reading from 5th record and stops at 15th record but instead SAS starts reading from 10th record and goes all the way to the end of the dataset up to 19th record. So, what is there I am missing here because I don't get the logic here at all?

SASHELP.CLASS dataset for reference

proc print data=sashelp.class;
run;

Re: Unusual result with FIRSTOBS and OBS option with WHERE statement

PaigeMiller — Thu, 10 Oct 2024 13:26:02 GMT

The PROC PRINT starts at the 5th male record and continues to the 15th male record (which doesn't exist).

Re: Unusual result with FIRSTOBS and OBS option with WHERE statement

Nipun22 — Thu, 10 Oct 2024 13:27:45 GMT

Can you please elaborate?

Re: Unusual result with FIRSTOBS and OBS option with WHERE statement

PaigeMiller — Thu, 10 Oct 2024 13:34:12 GMT

@Nipun22 wrote:
Can you please elaborate?

What needs elaboration? What is not clear in my previous reply?

Re: Unusual result with FIRSTOBS and OBS option with WHERE statement

yabwon — Thu, 10 Oct 2024 13:44:09 GMT

Maxim #1: Read the doc.

https://documentation.sas.com/doc/en/lrcon/9.4/n1iok7aawea9zzn1aso4ulosip7l.htm

WHERE takes precedence over OBS= and FIRSTOBS=.

If you comment out "OBS" part like this:

proc print data=SASHELP.CLASS/*(firstobs=5 obs=15)*/;
where Sex='M';
run;

the result will be:

And in the original (not commented-out code) this is the moment where FIRSTOBS=5 starts working, that is why you get:

and since there are less then 15 obs selected by the WHERE clause, you get them all.

Bart

Re: Unusual result with FIRSTOBS and OBS option with WHERE statement

Nipun22 — Thu, 10 Oct 2024 14:12:55 GMT

So it means that SAS will create a subset of the dataset using the where statement and then it will run firstobs and obs.
Also if the subset of the main dataset had more than 15 records then it would have stopped reading on 15th record? right?

Re: Unusual result with FIRSTOBS and OBS option with WHERE statement

yabwon — Thu, 10 Oct 2024 14:33:09 GMT

yes, exactly.

Re: Unusual result with FIRSTOBS and OBS option with WHERE statement

Astounding — Thu, 10 Oct 2024 14:42:49 GMT

This type of question has actually been around for 40 years, ever since the WHERE statement was invented. Either interpretation seems reasonable:

Consider observations 5 through 15, and select only the males
Consider only the males, and of those take the 5th through the 15th

In fact, originally SAS couldn't decide which interpretation to use. For a year or two, using WHERE when OBS/FIRSTOBS was in effect would generate an error message. Finally SAS decided that the second interpretation would be the more useful one.

Re: Unusual result with FIRSTOBS and OBS option with WHERE statement

Nipun22 — Thu, 10 Oct 2024 14:48:31 GMT

that's quite interesting! thanks for telling
Although i was hesitating initially to ask questions related on simple concepts like where statement etc but it seems it was logical.

Re: Unusual result with FIRSTOBS and OBS option with WHERE statement

Nipun22 — Thu, 10 Oct 2024 19:00:11 GMT

@PaigeMiller

try answering like this someday that will be more helpful