topic Re: Lag function and _n_ in SAS Programming

Lag function and _n_

Paul_NYS — Wed, 26 Mar 2014 13:37:05 GMT

Hi Everyone

I am using the below data step to set my tprfiled variable to the prior value for it except for the first record in the data set. However, it is not recognizing the first record's 0 when processing the second record--a null is inserted instead of 0. Any ideas why this is?

Paul

data s1astpr3;

set s1astpr2;

if _n_ ne 1 then tprfiled=lag(tprfiled);

run;

entity_id	tprfiled
1	0
2
3	0
4	0
5	0
6	0
7	0
8	0
9	0
10	0
11	0
12	0
13	0
14	0
15	0
16	0
17	0
18	0
19	0
20	1
21	1
22	0

Re: Lag function and _n_

pradeepalankar — Wed, 26 Mar 2014 13:48:30 GMT

Hi,

Try with just -> tprfiled=lag(tprfiled); it will give null value for first row and lag values for subsequent rows.

your code is giving the same value for tprfiled which must be 0 in your source data, and lagging null value to second row.

Re: Lag function and _n_

RW9 — Wed, 26 Mar 2014 13:50:15 GMT

Hi,

Not sure about lag, tried using it myself some time back and had some weird results. So this doesn't answer your question, but does do whats requested:

proc sql;

create table WANT as

select A.ENTITY_ID,

B.TPRFILED

from HAVE A

left join HAVE B

on A.ENTITY_ID=(B.ENTITY_ID+1);

quit;

Re: Lag function and _n_

Paul_NYS — Wed, 26 Mar 2014 14:00:12 GMT

I tried doing just doing just the lag initially, but wanted to accommodate the issue with the first record. But I just tried the below, which is a variation of this and it works:

data s1astpr3;

set s1astpr2;

tprfiled2=tprfiled;

tprfiled=lag(tprfiled);

if _n_ = 1 then do;

tprfiled=tprfiled2;

end;

drop tprfiled2;

run;

Re: Lag function and _n_

Paul_NYS — Wed, 26 Mar 2014 14:02:14 GMT

Hi Rw9

The only issue with this is that I have a lot more columns that I indicated and they change regularly, so I don't really want to deal with proc sql and writing out column names.

Paul