topic how to use first. last.? in SAS Procedures

how to use first. last.?

littlestone — Tue, 31 Jan 2012 22:17:24 GMT

Hello,

Suppose I have following dataset (" test"):

id	var_1	var_2
1	1	1
1	2	1
1	3	0
1	4	0
1	5	1
2	6	1
2	7	0
2	8	0
2	9	1
2	10	1

I run follwoing codes:

proc sort data=test;

by id var_1 var_2;

run;

data test;

set test;

by id var_1 var_2;

if last.var_2 then var_3=1;

else var_3=0;

run;

What I expect is:

id	var_1	var_2	var_3
1	1	1	0
1	2	1	1
1	3	0	0
1	4	0	1
1	5	1	0
2	6	1	1
2	7	0	0
2	8	0	1
2	9	1	0
2	10	1	1

However, what I get is:

id	var_1	var_2	var_3
1	1	1	1
1	2	1	1
1	3	0	1
1	4	0	1
1	5	1	1
2	6	1	1
2	7	0	1
2	8	0	1
2	9	1	1
2	10	1	1

What I did is wrong?

how to use first. last.?

Tom — Tue, 31 Jan 2012 22:45:12 GMT

The problem is the VAR_1 is different on every observation. So within the set of constant values for ID and VAR_1 every value of VAR_2 is unique.

data want ;

set test;

by id var_2 notsorted;

var_3 = last.var_2;

run;

how to use first. last.?

art297 — Tue, 31 Jan 2012 22:45:56 GMT

I think you are trying to do something like:

data test;

set test;

by id var_2 notsorted;

if last.var_2 then var_3=1;

else var_3=0;

run;

However, that would meet all of your expectations except for the 5th record which, if I correctly understand what you are trying to do, was incorrect in your example.

Re: how to use first. last.?

Tom — Tue, 31 Jan 2012 22:53:01 GMT

To get your requested output use BY VAR_2 NOTSORTED.

Not sure that actually makes any sense as it is crossing boundry between values of ID.

159  data want ;
160    set have ;
161    by var_2 notsorted;
162    var_3=last.var_2;
163    put (id var_1 var_2 var_3) (3.);
164  run;

1 1 1 0

1 2 1 1

1 3 0 0

1 4 0 1

1 5 1 0

2 6 1 1

2 7 0 0

2 8 0 1

2 9 1 0

2 10 1 1

how to use first. last.?

littlestone — Wed, 01 Feb 2012 03:00:44 GMT

Thank you all very much for help. I never know there is a "notsorted" option.

By the way, could you please elaborate why 5th record is incorrect? I couldn't figure it out myself...