Generating a moving sum variable in R

Question

I suspect this is a somewhat simple question with multiple solutions, but I\'m still a bit of a novice in R and an exhaustive search didn\'t yield answers that spoke well to wha

Answer 1

You can use filter in ddply (or any other function implementing the "split-apply-combine" approach):

library(plyr)
ddply(DF, .(country), transform, 
          x5yrsum2 = as.numeric(filter(x,c(0,rep(1,5)),sides=1)))

#    country year x x5yrsum x5yrsum2
# 1        A 1980 9      NA       NA
# 2        A 1981 3      NA       NA
# 3        A 1982 5      NA       NA
# 4        A 1983 6      NA       NA
# 5        A 1984 9      NA       NA
# 6        A 1985 7      32       32
# 7        A 1986 9      30       30
# 8        A 1987 4      36       36
# 9        B 1990 0      NA       NA
# 10       B 1991 4      NA       NA
# 11       B 1992 2      NA       NA
# 12       B 1993 6      NA       NA
# 13       B 1994 3      NA       NA
# 14       B 1995 7      15       15
# 15       B 1996 0      22       22