Intro R HBS debrief ideas

[michaellevy]

• ?seq challenge question: prepare people that didn't teach but need to learn (be explicit on this)
• indexes divisible by three challenge bonus question: needs a little more work or better phrasing
• more emphasis on c() function, its purpose and use
  • In introducing vectors, perhaps show several ways to create one
• Perhaps a graphic of $ and [] operations to illustrate what is happening
• Use message, warning, and stop to demo them. Prepares for messages returned with read_xxx.