I would like to change a vector of integers into their order of appearance.
Suppose I have this vector:
c(3, 2, 3, 4, 4, 5, 5, 2, 1)
The integer 3 appears first, so it should be 1.
The integer 2 appears second, so it should be 2. And so on.
The desired outcome:
1 2 1 3 3 4 4 2 6
You can coerce to factor with unique values as levels.
as.numeric(factor(x, levels=unique(x)))
# [1] 1 2 1 3 3 4 4 2 5
Data:
x <- c(3, 2, 3, 4, 4, 5, 5, 2, 1)
You can use match function to find the order of appearance of unique values:
x <- c(3, 2, 3, 4, 4, 5, 5, 2, 1)
match(x, unique(x))
[1] 1 2 1 3 3 4 4 2 5