dplyr HBS debrief ideas

[michaellevy]

In addition to #29 and #30:

• Can challenges be re-written to be a little clearer?
• I (ML) think an overarching subsection early on, clarifying especially the data.frame-centric nature of dplyr and tidyverse (always DF in; always DF out) might be helpful in general and with the tricky assignment of the data.frame vs assignment to a column within a data.frame. Also, “here are five fundamental tasks you’ll learn to do in data.frames. Dplyr has one function for each of these tasks.”
• Variance exercise: may need to reword parts to make more clear the goal of the exercise. "Can you make a plot that shows the distribution of country level gdp by without summarizing beforehand?"
• Consider changing variance to mean. Variance might be one weight too many for some.
• Graphic like PIPE graphic in SWC Unix materials
• Typo in code chunk in pipe section
• How prominent should the pipe be? Much disagreement about this. Also, how much should we make a point of nesting and repeated assigning vs. just demoing the "right" (piped) way to do things?