Use lapply with your own function

As Filip explained in the instructional video, you can use lapply() on your own functions as well. You just need to code a new function and make sure it is available in the workspace. After that, you can use the function inside lapply() just as you did with base R functions.

In the previous exercise you already used lapply() once to convert the information about your favorite pioneering statisticians to a list of vectors composed of two character strings. Let's write some code to select the names and the birth years separately.

The sample code already includes code that defined select_first(), that takes a vector as input and returns the first element of this vector.

Deze oefening maakt deel uit van de cursus

Intermediate R

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Oefeninstructies

Apply select_first() over the elements of split_low with lapply() and assign the result to a new variable names.
Next, write a function select_second() that does the exact same thing for the second element of an inputted vector.
Finally, apply the select_second() function over split_low and assign the output to the variable years.

Praktische interactieve oefening

Probeer deze oefening eens door deze voorbeeldcode in te vullen.

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

# Write function select_first()
select_first <- function(x) {
  x[1]
}

# Apply select_first() over split_low: names


# Write function select_second()




# Apply select_second() over split_low: years

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