差分といっても色々な考え方がある。
> x = 1:5 > x [1] 1 2 3 4 5
> lag(x) [1] NA 1 2 3 4
> lead(x) [1] 2 3 4 5 NA
> diff(x) [1] 1 1 1 1
> diffinv(x) [1] 0 1 3 6 10 15 > diffinv(x, xi = 0) [1] 0 1 3 6 10 15 > diffinv(x, xi = 10) [1] 10 11 13 16 20 25
> cumsum(x) [1] 1 3 6 10 15