To use the functions in an add-on package you first need to install the package. Remember you only need install it once.
During the writing of the book, and in early 2018 the normal method for installing the ggfortify add-on package didn’t work (we got the message package ggfortify is not available (for R Version 3.2.4)).
This has not happened for some time, so hopefully you won’t experience it. If you do…
As the Second Edition of Getting Started with R was going to press, Rstudio changed the function it uses to import data in the Import Dataset tool, from the base function read.csv() to the read_csv() function in the readr package. Since then, the Import Dataset button gives a menu with an option to use either (“base” uses read.csv and “readr” uses read_csv) From the Rstudio Blog about the readr package: