How to obtain previous observation by id

sasphd — Fri, 13 Jan 2023 17:40:07 GMT

Hello,

Have

secid sas_date TNA

1 201501 345

1 201502 234

2 201501 278

2 201502 876

want

secid sas_date TNA

1 201501 .

1 201502 345

2 201501 .

2 201502 278

Re: How to obtain previous observation by id

ballardw — Fri, 13 Jan 2023 17:47:51 GMT

It really is a good idea to be consistent about use of variable names. You said "by id" which makes me guess that you mean secid variable. Having to guess can result in poor performance.

One way: This adds a new variable Ltna so you can compare the results for accuracy.

data want;
   set have;
   by notsorted secid;
   ltna= lag(tna);
   if first.secid then call missing(ltna);
run;

The By statement assumes your data is at least grouped by Secid if not sorted by such. The By statement makes automatic variables that indicate whether the current record is either the first or last of a by group.

The Lag function returns values from the previous record with some limitations. The above approach always gets a previous value and then sets it to missing when it is the first of Secid group.

topic How to obtain previous observation by id in SAS Procedures

How to obtain previous observation by id

Re: How to obtain previous observation by id