We have now successfully imported the data and looked at some important high-level statistics that provided us with a basic understanding of what values are in the dataset and how frequently some features appear. With this recipe, we continue the exploration by looking at some of the fuel efficiency metrics over time and in relation to other data points.
Analyzing automobile fuel efficiency over time
Getting ready
If you completed the previous recipe, you should have everything you need to continue.
How to do it...
The following steps will use both plyr and the graphics...