topic Re: Delete cases who don't have before and after readings in SAS Programming

Delete cases who don't have before and after readings

Jordani — Wed, 28 Sep 2016 03:28:56 GMT

Hi,

I have a longitudinal data on Patients with hypertension receiving a certain treatment. I would include the patient in the analysis , if and only if, he has two readings of blood pressure , one before treatment and one after. The data look like this

ID BloodPressure Time

1 110 Before

1 90 After

1 98 After

2 90 After

2 89 After

3 95 Before

3 97 After

4 100 before

4 98 Before

5 89 After

As you can see , Pateints number 2 and 4 Will not be included as they don't have readings before and after. Patient number 5 will also be deleted as he only have one reading

I only managed to delete cases with one reading using the command .

Data new ;

set Have;

By ID;

If FIRST.ID and LAST.ID then delete;

run;

Any suggestions ?

Re: Delete cases who don't have before and after readings

PGStats — Wed, 28 Sep 2016 04:20:26 GMT

Use a SQL query:

data have;
input ID     BloodPressure   Time :$8.;
datalines;
1        110                    Before
1         90                     After          
1         98                     After
2         90                      After
2         89                      After
3         95                      Before
3          97                     After
4          100                   before   
4           98                    Before 
5           89                    After 
;

proc sql;
create table want as
select * from have
group by ID
having count(distinct upcase(time)) > 1;
select * from want;
quit;

Re: Delete cases who don't have before and after readings

Jordani — Wed, 28 Sep 2016 04:44:22 GMT

Thank you PG , I used it and it worked .

Re: Delete cases who don't have before and after readings

ballardw — Wed, 28 Sep 2016 17:49:26 GMT

Be advised that the code that @PGStats provided counts levels not values. If for some reason you end up with something like Atfer, Bfeore or other spellings or words like missing then it well include those.

Re: Delete cases who don't have before and after readings

PGStats — Wed, 28 Sep 2016 18:05:51 GMT

Yeah. I guess that counting DISTINCT UPCASE(FIRST(time)) would be a bit more robust.

Re: Delete cases who don't have before and after readings

Jordani — Wed, 28 Sep 2016 19:35:12 GMT

I have done both of them and end with same results. I created the Time variable myself, so I would not expect to have misspellings or errors. However, it's a valuable advice , I will take it into consideration in other analyses.

Thank you