Find first and last non-missing value by group

[hua]

Hello All,

I tried to find the first and last non-missing value in a dataset by group, but still have some trouble to do so. I hope someone in the SAS community groups can help. Thanks a lot!

I have a dataset looks like this:

stn	year	month	day	var
1	2000	12	29	0.5
1	2000	12	30	.
1	2000	12	31	0
1	2001	1	1	0.2
1	2001	1	2	1
1	2001	1	3	.
2	2000	12	29	.
2	2000	12	30	.
2	2000	12	31	.
2	2001	1	1	0
2	2001	1	2	1.5
2	2001	1	3	3

And I want to find the first and last non-missing observation(var) for each stn so that I could know the nonmissing var for each stn is from what time to when. What I means is, in this example, I want to find for stn 1 the first is in 12/29/2000 and the last is 1/2/2001. And for stn 2, the first is 01/01/2001, and the last is 01/03/2001.

If any one can assist in this problem I would greatly appreciate it!

Thank you and anxiously awaiting a reply!

[Astounding · Accepted solution]

SAS has tools that make this easy:

data want;

set have;

by stn;

where var > .;

if first.stn or last.stn;

run;

The combination of WHERE + BY sets up the BY variables based on the observations that meet the WHERE condition.

[hua]

It works! Thank you so much!