Thanks for finding this @ssimon. I'll need to change it: What you are looking at is an HTML tutorial made with the learnr package. AFAIK, learnr tutorials do not have a way to open the R data viewer, which is what View() opens. If you run the code (including install.packages("babynames") and library(babynames) in an R console, it should work. As you may now guess, the content for some of the tutorials pre-exists the finished version of learnr.