The apply family

Question 1

Which function turns a list into a vector?

Answer 1

unlist()

Ex: unlist(my_list)

Question 2

Which function applies the given function to every element of the inputted vector or list, returning a list?

Answer 2

lapply()

Ex: lapply(my_vector, my_func)

Question 3

Which function applies the inputted function to every element of the inputted vector, before simplifying the result if possible into a vector or matrix?

Answer 3

sapply()

Ex: sapply(my_vector, my_func)

Question 4

Which function applies the inputted function to every element of the inputted vector, before simplifying the result, requiring the format of the inputted function to be explicitly inputted?

Answer 4

vapply()

Ex: vapply(my_vector, max, numeric(1))

Question 5

Which function is safer, vapply or sapply?

Answer 5

vapply is safer because by forcing you to specify the return type of the inputted function, vapply essentially forces you to think about whether the output will ultimately be a vector, matrix, or list.