Do you just want to code the table up? Would something like this suffice?:
PCP <- c(0, 4.9, 5, 9.9, 10, 14.9, 15)
seq2max <- seq(0,max(PCP)+5,5)
result <- data.frame(min=seq2max,max=seq2max+4.9,DRI=seq_along(seq2max)-1)
min max DRI
1 0 4.9 0
2 5 9.9 1
3 10 14.9 2
4 15 19.9 3
5 20 24.9 4
result$DRI
# [1] 0 1 2 3 4
9
solved Creating Index Variable in R [duplicate]