This is a bit trivial but how can i generate the set of numbers in x not included in the sample.
x=rnorm(6,0,1)
k=sample(x,3)
Rather than sampling the values, sample the indexes.
set.seed(15)
(x <-rnorm(6,0,1))
# [1] 0.2588229 1.8311207 -0.3396186 0.8971982 0.4880163 -1.2553858
idx <- sample(length(x),3)
(selected <- x[idx])
# [1] 0.8971982 -1.2553858 0.4880163
(notselected <- x[-idx])
# [1] 0.2588229 1.8311207 -0.3396186