Warning Message about suggested packages in tutorials

[bjcoleman]

The data package NHANES is a suggested package for the tutorial, and so the command learnr::run_tutorial("introduction", package = "ggformula") produces the message Error in library(NHANES) : there is no package called ‘NHANES’ when the package is not installed.

This is confusing for new users. Instead, it would be helpful to check for the packages when the tutorial is launched and produce a warning message.

[nicholasjhorton]

That's a great suggestion. We will investigate.

[rpruim]

I've decided to solve this by eliminating the hard dependency. NHANES will only be available in the exercise at the end if you have it installed on your system.

[rpruim]