3.1 Aperitif

Palmer Penguins

3.1.1 Counting Penguins

Consider this code to count the number of Gentoo penguins in the penguins data set. We see that there are 124 Gentoo penguins.

sum("Gentoo" == penguins$species)
# output: 124

3.1.2 In

One subtle error can arise in trying out %in% here instead.

species_vector <- penguins |> select(species)
print("Gentoo" %in% species_vector)
# output: FALSE

Where did the penguins go?

3.1.3 Fix: base R

species_unlist <- penguins |> select(species) |> unlist()
print("Gentoo" %in% species_unlist)
# output: TRUE

3.1.4 Fix: dplyr

species_pull <- penguins |> select(species) |> pull()
print("Gentoo" %in% species_pull)
# output: TRUE

3.1.5 Motivation

• What are the different types of vectors?
• How does this affect accessing vectors?

Side Quest: Looking up the %in% operator

If you want to look up the manual pages for the %in% operator with the ?, use backticks:

?`%in%`

and we find that %in% is a wrapper for the match() function.