topic Counting the number of patients and frequencies for other categorical variables per study arm in SAS Programming

Counting the number of patients and frequencies for other categorical variables per study arm

PaulaC — Fri, 02 Dec 2016 17:55:23 GMT

Hello,

I have a clinical trial dataset and am trying to determine the frequencies of a few categorical variables as well as the number of unique patients per study arm at baseline.

I had initially done proc freq, but since I have multiple rows for each patient due to multiple visits per patient I was told that for proc freq there should only be one row/person. So, the values I got were a count of the same patient numerous times. I was told that I could use the where statement to only get the frequency at the baseline visit, but that did not work either. No observations were read.

My code is below:

proc freq data=xxxxl;
where visit="001";
tables race*group sex*group /norow nopercent;
run;

I received the following message in the log: NOTE: No observations were selected from data set xxx.
NOTE: There were 0 observations read from the data set xxx.
WHERE visit='001'

I am not sure what I did wrong and what I need to do to get the correct answer.

I am expecting the output to look as follows:

Group 1 Group 2

xxx xxx (these numbers would the number of unique patients in each group)

Race Group 1 Group 2

White xxx xxx

Black xxx xxx

Other xxx xxx

Any help would be greatly appreciated.

Thanks

Re: Counting the number of patients and frequencies for other categorical variables per study arm

mkeintz — Fri, 02 Dec 2016 18:01:21 GMT

Visit is a character variable?

Then do a proc freq of visit to see what values it actually has in the data step.

And also note;

where visit='001' will NOT match a right-justified 4-byte visit value of ' 001' (note leading space). If that's the problem, then either

where visit=' 001'

where left(visit)='001'

Re: Counting the number of patients and frequencies for other categorical variables per study arm

PaulaC — Fri, 02 Dec 2016 19:45:52 GMT

Yes, visit is a character variable. I strip(visit)="001.00" and I got a result but it did not seem to subset the data to give the counts with only one observation per patient. The number I got was much more than it should be. Thanks.

Re: Counting the number of patients and frequencies for other categorical variables per study arm

mkeintz — Fri, 02 Dec 2016 20:01:35 GMT

If you get fewer "001.00" cases than expected, then perhaps the original visit coding has errors or incosistencies. I think you have to find a patient with no visit="001.00" to see whether there are other codes indicating baseline visit.

Re: Counting the number of patients and frequencies for other categorical variables per study arm

PGStats — Sat, 03 Dec 2016 05:14:50 GMT

Assuming your data is sorted by some patient_Id variable, try keeping the first record for each patient:

data patients;
set xxxxl;
by patient_Id;
if first.patient_Id;
run;

proc freq data=patients;
tables race*group sex*group /norow nopercent;
run;

Re: Counting the number of patients and frequencies for other categorical variables per study arm

PaulaC — Fri, 09 Dec 2016 21:21:53 GMT

Thank you for your suggestion. I will try that.