Creating the second lag in a panel data set

[bssturgi]

I have panel data, and I am trying to create lags. The code below seems to be generating the desired results for the first lag of the variable of interest.

proc sort data=Pooled_Panel;
by Country Year;
run;

data Pooled_Panel_lags;
set Pooled_Panel;
by Country Year;
Lag_EFWS=Lag(EFWS);
If First.Country then do;
   Lag_EFWS=.;
end;
run;

My question is this.  How do I do this for the second lag?  I know to use Lag2(variable), but what type of if-then statement do I need here?  I don't want the second lag to be the value two rows before if that value corresponds to another country.  I'm using SAS 9.4.

[Reeza]

Do you have SAS/ETS? If so, you can do this a bit more easily with the convert statement. 

If you don't, you're stuck with a counter. Create a counter variable using RETAIN and then delete any less than what you need.

data Pooled_Panel_lags;
set Pooled_Panel;
by Country Year;

Lag_EFWS  = Lag(EFWS);
Lag_EFWS2 = Lag2(EFWS);
 
If First.Country then counter=0;

counter+1;

if counter <= 1 then call missing(lag_efws, lag_efws2);
if counter <= 2 then call missing(lag_efws2);



run;

I can't test it, but this may work as well, make sure to only Keep what you need in each data set.

data want;
merge pooled_panel
           pooled_panel (firstobs=2 rename = (efws = lag_efws) keep=(PUT VARIABLE LIST HERE))
           pooled_panel (firstobs=3) rename = (efws = lag_efws2) keep=(PUT VARIABLE LIST HERE));

by country;

run;

[bssturgi]

Thank you!  The code you provided with the counter has done the trick.

I don't have SAS/ETS, but I think one of my colleagues may have at, and I may get it in the future.  Could you tell me how I would do this with the convert statement?

[Reeza]

The documentation has examples, with one exactly calculating lag1 and lag2.

http://documentation.sas.com/?docsetId=etsug&docsetVersion=14.3&docsetTarget=etsug_expand_examples04...