map() and Typed Variants
Apply functions over lists with map(), map_dbl(), map_chr(), and map_lgl().
Functional Programming with purrr
The purrr package provides consistent, type-safe tools for functional programming in R. Instead of writing for loops, you map a function over a list or vector. The result is cleaner code that's easier to reason about and compose.
library(purrr)
# A list of numbers
numbers <- list(1, 4, 9, 16, 25)
# Apply sqrt() to each element
result <- map(numbers, sqrt)
print(result)map() — Always Returns a List
map(.x, .f) applies function .f to each element of .x and returns a list. The input can be a list, vector, or data frame (iterates over columns). This is the most general map variant.
library(purrr)
# Map over a character vector
fruits <- c('apple', 'banana', 'cherry')
# nchar() counts characters in each string
result <- map(fruits, nchar)
print(result) # Returns a list
print(class(result))