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Use lapply with additional arguments

In the video, the triple() function was transformed to the multiply() function to allow for a more generic approach. lapply() provides a way to handle functions that require more than one argument, such as the multiply() function:

multiply <- function(x, factor) {
  x * factor
}
lapply(list(1,2,3), multiply, factor = 3)

On the right we've included a generic version of the select functions that you've coded earlier: select_el(). It takes a vector as its first argument, and an index as its second argument. It returns the vector's element at the specified index.

This is a part of the course

“Intermediate R”

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Exercise instructions

Use lapply() twice to call select_el() over all elements in split_low: once with the index equal to 1 and a second time with the index equal to 2. Assign the result to names and years, respectively.

Hands-on interactive exercise

Have a go at this exercise by completing this sample code.

# Definition of split_low
pioneers <- c("GAUSS:1777", "BAYES:1702", "PASCAL:1623", "PEARSON:1857")
split <- strsplit(pioneers, split = ":")
split_low <- lapply(split, tolower)

# Generic select function
select_el <- function(x, index) {
  x[index]
}

# Use lapply() twice on split_low: names and years
Edit and Run Code