依次为值创建一个“运行ID”

我有一个包含重复整数有序序列的向量：

x <- c(1, 1, 1, 2, 2, 2, 2, 3, 3, 5, 5, 5, 5, 6, 6, 9, 9, 9, 9)

I want to create a "run ID" (I assume using data.table::rleid()) for numbers that are in sequence. That is, numbers which are either equal or +1 the previous value.

因此，预期输出为：

x
#> [1] 1 1 1 2 2 2 2 3 3   5 5 5 5 6 6   9 9 9 9
data.table::rleid(???)
#> [1] 1 1 1 1 1 1 1 1 1   2 2 2 2 2 2   3 3 3 3

My first thought was to simply check if each value is the same or +1 the previous, but that doesn't work since the first change is considered a run of its own, obviously (a FALSE surrounded by TRUEs):

x
#> [1] 1 1 1 2 2 2 2 3 3   5 5 5 5 6 6   9 9 9 9
data.table::rleid((x - lag(x, default = 1)) %in% 0:1)
#> [1] 1 1 1 1 1 1 1 1 1   2 3 3 3 3 3   4 5 5 5

我显然需要一些东西，使我可以将每个值与最后一个不同的值进行比较，但是我无法考虑如何有效地做到这一点。有指针吗？