addition lag operator

[rajat051984]

I have the following dataset. 

data input;
input trans_yearmon 8. rv_acct 5.2  factor 8.2   ;
datalines;
201506 0.21 
201507       -0.62
201508       1.65
201509       0.09
201510       0.28
;
run;

I want rv_act to be = lag(rv_act) + factor.
So the new dataset should look as follows -

	B	C	D	E
1		rv_acct	factor	rv_acct_formula
2	201506	0.21
3	201507	-$0.41	-$0.62	C3 = C2 + D3
4	201508	$1.24	$1.65	C4 = C3 + D4
5	201509	$1.33	$0.09	C5 = C4 + D5
6	201510	$1.61	$0.28	C6 = C5 + D6

Can you kindly tell me how to do it in SAS ? I was using 'lag operator' but that was not helpful ..  

-Rajat

[Reeza]

Lag is correct methodology. Post your code that didn't work. 

[Reeza]

Sorry, just use retain. 

Retain rv_acct;

rv_account+factor;

This should be a new variable in the dataset otherwise you might get unexpected results. 

[Ksharp · Accepted solution]

data input;
input trans_yearmon  rv_acct  factor   ;
datalines;
201506 0.21  .
201507   .    -0.62
201508  .     1.65
201509    .   0.09
201510   .    0.28
;
run;
data want;
 set input;
 retain lag;
 if _n_=1 then lag=rv_acct ;
  else do;
   rv_acct=lag+factor;lag=rv_acct;
  end;
drop lag;
run;