Ronan Harrington executes a function for each row in a dataframe:
In this section, we want to tidy the different types of flight in the data set by increasing the number of rows and decreasing the number of columns. For a given airport on a given day, instead of having multiple columns/variables for arrivals, departures and total number of flights, we want to have one column describing the flight type (e.g. arrival or departure) and one column with the value of that flight type/number of flights. This will give the data set a tidy structure.
Click through for the process and the script. H/T R-Bloggers.