number of days in the study period

[jenim514]

Hi! I need help calculating the number of actual days a person was in my 5 year study.  So, looking accross observations, I need to calculate number of days between the first encounter date 'encdate' and last encounter date by 'patientid'.

Assistance is apprecited!

[Reeza]

Please post sample input and output data.

[Astounding · Accepted solution]

Here's one approach.

proc summary data=have nway;

class patientid;

var encdate;

output out=durations (keep=patientid firstday lastday) min=firstday max=lastday;

run;

This gives you a data set with three variables in it, and one observation per patientid.  You can use that in a DATA step, and apply whichever formula you wish:

duration = lastday - firstday;

duration = lastday - firstday + 1;

The SQL programmers out there can do this in one step, but SQL isn't my strong point.

[ballardw]

Minor change to @Astounding solution:

output out=durations (keep=patientid firstday lastday) range=;

Range will basically do the max-min.

[kvemulapalli571]

how can i get sas software

[kvemulapalli571]

please help me how can i get sas software

[Reeza]

@kvemulapalli571

1. Please post your questions in a new discussion rather than in someone else's question

2. Google "SAS University Edition" -> This is a free version of SAS available for learning purposes only. You need a 64bit machine. 

    Or use SAS Academics on Demand -> Independent Learners option.