The “map_at” Function in R

• Package: purrr

• Purpose: Apply a function to specified elements or positions within a list or vector.

• General class: Function

• Required argument(s):

• .x: The list or vector to be processed.

• .at: The positions or indices of elements to which the function should be applied.

• .f: The function to apply to the specified elements.

• Notable optional arguments:

• .else: A function or value to apply to elements that are not specified. If not specified, elements that are not selected remain unchanged.

• .progress: A logical or function to show progress, useful for long computations.

• Example:

• # Load the required library
  library(purrr)
  
  # Define a list of numeric vectors
  list_data <- list(c(1, 2, 3), c(4, 5, 6), c(7, 8, 9))
  
  # Define a function to add 10
  add_10 <- function(x) {x + 10}
  
  # Apply the function only to the first and third elements in the list
  results <- map_at(list_data, c(1, 3), add_10)
  
  # Print the results
  print(results)

• In this example, map_at from the purrr package is used to apply add_10 to the first and third elements in list_data. The result is a list where only the specified elements (positions 1 and 3) are modified by the add_10 function, while the other elements remain unchanged.