Read the source code for each of the following three functions, explain what they do. ( R STUDIO)

f1 <- function(string, prefix) { substr(string, 1, nchar(prefix)) == prefix } f2 <- function(x) { if (length(x) <= 1) return(NULL) x[-length(x)] } f3 <- function(x, y) { rep(y, length.out = length(x)) }