Rescale Vector R

r, vector

Solution

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

Problem

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).

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