remove the last element of a vector

Question

I need to remove the last number in a groups of vectors, i.e.:

v <- 1:3
v1 <- 4:8

should become:

v <- 1:2
v1 <-         


        

Answer 1

This is another option, which has not been suggested before. NROW treats your vector as a 1-column matrix.

v[-max(NROW(v))]#1 2
v1[-max(NROW(v1))]#4 5 6 7

Based on the discussion above, this is (slightly) faster then all the other methods suggested:

x <- rnorm(1000)
system.time(replicate(50000, y <- head(x, -1)))
user  system elapsed 
3.446   0.292   3.762
system.time(replicate(50000, y <- x[-length(x)]))
user  system elapsed 
2.131   0.326   2.472
system.time(replicate(50000, y <- x[-max(NROW(x))]))
user  system elapsed 
2.076   0.262   2.342