topic Re: Lag function help in SAS Programming

Lag function help

ywon111 — Tue, 26 Jul 2022 06:33:50 GMT

I am trying to create a dataset so an individual ID will get one row only based on the count of pens and pencils. Maybe this can be solved by the lag function?

data have;
input ID Pens Pencil;
infile datalines missover;
datalines;
1 1 0
2 1 0
3 1 0
4 1 0
5 1 0
5 0 3
6 0 1
;

data want;
input ID Pens Pencil;
infile datalines missover;
datalines;
1 1 0
2 1 0
3 1 0
4 1 0
5 1 3
6 0 1
;

Re: Lag function help

Patrick — Tue, 26 Jul 2022 06:49:06 GMT

One option

proc means data=have noprint nway;
  class id;
  var pens pencil;
  output out=want(drop=_:) sum= /keeplen;
run;

Re: Lag function help

Tom — Tue, 26 Jul 2022 15:36:56 GMT

Why would you use the KEEPLEN option? Even if the values of those variables are small enough that they will not lose precision when stored in less than the full 8 bytes it is not guaranteed that the SUM will also fit into that smaller space.

KEEPLEN

specifies that statistics in the output data set inherit the length of the analysis variable that PROC MEANS uses to derive them.

CAUTION

You permanently lose numeric precision when the length of the analysis variable causes PROC MEANS to truncate or round the value of the statistic. However, the precision of the statistic matches that of the input.

Re: Lag function help

Patrick — Tue, 26 Jul 2022 22:53:14 GMT

@Tom

Fair point and agree with what you say. Unfortunately I can't amend the code in the accepted solution anymore to not "propagate" something sub-optimal.