03-functions-for-data-notes.md

Instructor notes for "Functions for data"

Starting with this part of the lesson, the instructor should explain what the chunks of code do.

We start from a list of files (one file per country). The first step/function gathers the content of all the files into a single data frame (gather_gdp_data()). We use this function to demonstrate how it can be generalized to work in other contexts by using path and gdp-percapita- as arguments to the function. This can also be used to exemplify how writing functions can save time in the long term, as functions can be re-used across projects (but with the warning that it's easy here because all the files have exactly the same number of columns and are in the same order, which might not be the case in a real life case).

make_csv()

Demonstrate how to write this function. Start by just typing the write.csv line and expends from there. We use row.names=FALSE because we don't want them in the output, verbose just write something at the terminal which will be useful when we are building the full manuscript to keep track of progress. You may want to leave out the ... depending on the participants' level of comfort with R code.

Before the challenge of converting into functions

Demonstrate what the 2 chunks of code do before asking participants to convert them into functions.