Retain and lag function in R as SAS

Question

I am looking for a function in R similar to lag1, lag2 and retain functions in SAS which I can use with data.tables.

I know th

Answer 1

here's an example: cumulate value with sqldf:

> w_cum <-
 sqldf("select t1.id, t1.SomeNumt, SUM(t2.SomeNumt) as cum_sum
       from w_cum       t1
       inner join w_cum t2 on t1.id >= t2.id
       group by t1.id, t1.SomeNumt
       order by t1.id

")

   id SomeNumt cum_sum

• 1 11 11
• 2 12 23
• 3 13 36
• 4 14 50
• 5 15 65
• 6 16 81
• 7 17 98
• 8 18 116
• 9 19 135
• 10 20 155