Suppose I have a vector of integers such as:
> x
[1] 1 1 1 4 4 13 13 14
I am looking for an efficient way in R to rescale the vector to integers 1 to the max of the unique number of elements. Therefore the resulting vector would be:
1 1 1 2 2 3 3 4
Seems like a simple problem but I'm having trouble finding an efficient way to do it. In practice this vector is large (around 500).
Try match(x, sort(unique(x))):
x <- sample(1:50, 1e6, replace = TRUE)
benchmark(as.integer(factor(x)), match(x, sort(unique(x))),
replications = 20, columns = c("test", "elapsed", "relative"))
# test elapsed relative
# 1 as.integer(factor(x)) 18.44 10.36
# 2 match(x, sort(unique(x))) 1.78 1.00
identical(as.integer(factor(x)), match(x, sort(unique(x))))
# [1] TRUE
Try the following command, assuming that v is your vector
rank( v )
see ?rank for more information.
Well, this does give another result, but is correct as ranking, which is what I thought you want to achieve. To get your preferred result, do
as.integer( factor( v ) )
