HW6: Summary of the “MPG” Dataset from the “ggplot2” Package
William Stein
11/23/2019
Data description
The data set which is being analyzed within this R Markdown document will be the the “MPG” data set obtained from the “ggplot2” library. This data set consists of 234 rows and 11 columns. The data in each column consist of the car manufacturer, model, year, highway/city mpg, etc. Below is a table consisting of all of the variables and a desciption of the type of data contained under each column.
Summary Data Table:
| Variable | Description |
|---|---|
| manufacturer | The company who is responsible for making the vehicle |
| model | The model of the car |
| displ | The displacement or engine size of the engine in the standard model of the vehicle (in liters) |
| year | The model year of the vehicle |
| cyl | The number of cylinders in the vehicle’s engine |
| trans | The type of transmission inside of the vehicle (manual or automatic) |
| drv | “drv” stands for “drivetrain” which is either forward, rear, or 4-wheel drive |
| cty | The number of city miles per gallon that the car is able to achieve |
| hwy | The number of highway miles per gallon that the car is able to achieve |
| fl | The vehicle’s fuel type |
| class | The “type” of the vehicle (ex: compact, subcompact, midsize, etc.) |
Data Visualizations - Plot #1
Description and Interpretation of First Plot
The first plot (seen above) shows the combined average car MPG per manufacturer. That is, the average combined MPG across all car models per manufacturer were computed, and graphed depicted in the form of a bar chart. These variables were chosen to show a more general relationship between average combined MPG across all car models from the same manufacturer, summarized by manufacturer. It may be infered that Honda has the best fuel efficiency across all models, while Land Rover has some of the worst.
Data Visualizations - Plot #2
Description and Interpretation of Second Plot
The second plot (pictured above) illustrates every car’s combined MPG vs. its class; for example, Ford, Dodge, Chevrolet, etc. In addition, each dot, which represents a vehicle, is color coded to match the vehicle’s make. Such variables were chosen to depict the general trend that smaller cars generally gain higher fuel economies as opposed to larger cars. In general, it may be concluded that SUV’s have some of the worst fuel efficiency’s, while compact and subcompact cars rank as some of the best.