Related tools

• while(condition) action: performs action while condition is TRUE.

• repeat(action): repeats action forever (i.e. until it encounters break).

• Note that for can be rewritten as while and while can be rewritten as repeat (this goes in one direction only!); however:

Good practice is to use the least-flexible solution to a problem, so you should use for wherever possible. BUT you shouldn’t even use for loops for data analysis tasks as map() and apply() already provide less flexible solutions to most problems. (More in Chapter 9.)

for (i in 1:5) {
  print(i)
}
#> [1] 1
#> [1] 2
#> [1] 3
#> [1] 4
#> [1] 5

x_option <- function(x) {
  switch(x,
    a = "option 1",
    b = "option 2",
    c = "option 3"#,
    #stop("Invalid `x` value")
  )
}

i <- 1

while(i <=5 ) {
  print(i)
  i <- i+1
}
#> [1] 1
#> [1] 2
#> [1] 3
#> [1] 4
#> [1] 5

i <- 1

repeat {
  print(i)
  i <- i+1
  if (i > 5) break
}
#> [1] 1
#> [1] 2
#> [1] 3
#> [1] 4
#> [1] 5

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