why i cannot get rid of the second or third records of the same person

[Bal23]

data ab2 dup;

set ab1;

by id date;

if first.date then output ab2;

else output dup;

run;

A patient has multiple visits and I only need to see the first vist. But with the above code, I cannot find any duplicate records.

ANy advice how to remove the same ID with later visits, that might be second, third or even more visits?

Thanks.

[RW9]

You haven't shown your data, but I assume from the code that each row of data has a different value in DATE variable.  Therefore when:

if first.date 

Is evaluated every row is different.  Do you not have a visit variable, i.e. VISIT 1, VISIT 2 etc. you could use that.  Or if the DATE variable is actually a datetime then use datepart() function to use only the date.  Without further information on your data I can't say.

[Bal23]

yes each row of data has a different value in date variable

I do not have a visit variable, and date variable is a datetime,

can you provide a sas sample code as how to use datepart( )?

Thanks

[ballardw · Accepted solution]

If you want one per ID then use

if first.id then output ab2;

else output dup;