Value start from begining

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Frequent Contributor
Posts: 84

Value start from begining

data have;
input number;
cards;
12
10
8
6
4
2
run;

data want;
set have;
lag_d = lag(number) - number;
run;

when i run this code i am getting like this

 Obs number lag_d 1 12 . 2 10 2 3 8 2 4 6 2 5 4 2 6 2 2

but i need the ouput like this insted of staring . i need the valus from frist row

 Obs number lag_d 1 12 2 2 10 2 3 8 2 4 6 2 5 4 2 6 2 0

Accepted Solutions
Solution
‎03-31-2017 02:10 PM
Super User
Posts: 10,850

Re: Value start from begining

```
data have;
input number;
cards;
12
10
8
6
4
2
;
run;

data want;
merge have have(keep=number rename=(number=_n) firstobs=2);
lag_d=number-_n;
if missing(lag_d) then lag_d=0;
drop _n;
run;

```

All Replies
PROC Star
Posts: 1,403

Re: Value start from begining

What you want to do is to simulate a lead function. It can be done like this

``````data have;
input number;
cards;
12
10
8
6
4
2
run;

data have;
set have;

if eof=0 then
set have (firstobs=2 keep=number rename=(number=lead_number)) end=eof;

run; ``````

Bear in mind though, that the last value of your lag_d variable will be missing with this solution, which I think is more approprate than it being zero, since you do not know the next value of number. This can be corrected fairly easily though

Solution
‎03-31-2017 02:10 PM
Super User
Posts: 10,850

Re: Value start from begining

```
data have;
input number;
cards;
12
10
8
6
4
2
;
run;

data want;
merge have have(keep=number rename=(number=_n) firstobs=2);
lag_d=number-_n;
if missing(lag_d) then lag_d=0;
drop _n;
run;

```
☑ This topic is solved.