Replace missing values with previous values

[twildone]

Hi....I am trying to replace the missing values for the Start Date and Completion Date with the previous non missing dates and can't seem to get it to work. Any suggestions...thanks

StudentStatusID	StudentUID	Programs	CompletionDate	StartDate	q
68509	16710	Technical Drafting	2014-06-20	2013-09-05	2013-09-05
68509	16710	Technical Drafting	2014-06-27	2013-09-02	2013-09-02
68509	16710	Technical Drafting	2014-06-20	2013-07-02	2013-07-02
68509	16710	Technical Drafting	2014-06-20	2013-07-02
68509	16710	Technical Drafting	2014-06-20	2013-07-02
68509	16710	Technical Drafting	2014-06-20	2013-07-02
68509	16710	Technical Drafting	2014-06-20	2013-07-02
68509	16710	Technical Drafting	2014-06-20	2013-07-02
68509	16710	Technical Drafting	2014-06-20	2013-07-02	2013-07-02
68509	16710	Technical Drafting	.	.	.
68509	16710	Technical Drafting	.	.	.

proc sort data=StudentList26a;
by StudentUID StudentStatusID Programs descending StartDate;
run;

data StudentList26c;
do until(last.StudentUID);
set StudentList26a;
by StudentUID StudentStatusID Programs StartDate notsorted;
if last.StartDate and not missing(StartDate) then do;
q = StartDate;
end; 
if missing(StartDate) then do;
StartDate=q;
end; 
output;
end;
run;

[PaigeMiller]

You can use the RETAIN statement to achieve the result you want. See SAS help for examples.

You could also probably use the LAG statement.

[Astounding · Accepted solution]

I'm not sure you should be sorting in DESCENDING order, but that part is up to you.  Once you have sorted, here is an easy way:

data want;

update have (obs=0) have;

by StudentStatusID StudentUID Programs;

output;

run;