Lagged Variables in R

Question

I am trying to use R to develop a corporate financial model.

The model includes various line items, X, of the following form with actual values for time period 1, 2.. n and projected values for periods n+1, n+2,.. n+k. g is the average growth rate for the forecast period.

I need to construct a vector of the following form:

  X=c(X1,X2,...,Xn,Xn+1=(1+g)Xn,Xn+2=(1+g)Xn+1,...,Xn+k=(1+g)Xn+k-1))

How would I do this in R?

I have tried looking up the R literature on lagged variables but could not find a simple example which does what is required. I look forward to any guidance that can be given.

Answer 1

Does this do what you want?

x1 <- 1:10
g <- .1
x2 <- cumprod(c(tail(x1, 1), rep(1+g, 5)))
c(x1, x2)