Linear Models and Residuals for 'mtcars'

The data was extracted from the 1974 Motor Trend US magazine, and comprises fuel consumption and 10 aspects of automobile design and performance for 32 automobiles (1973–74 models).

data(mtcars)
summary(mtcars)

      mpg             cyl             disp             hp       
 Min.   :10.40   Min.   :4.000   Min.   : 71.1   Min.   : 52.0  
 1st Qu.:15.43   1st Qu.:4.000   1st Qu.:120.8   1st Qu.: 96.5  
 Median :19.20   Median :6.000   Median :196.3   Median :123.0  
 Mean   :20.09   Mean   :6.188   Mean   :230.7   Mean   :146.7  
 3rd Qu.:22.80   3rd Qu.:8.000   3rd Qu.:326.0   3rd Qu.:180.0  
 Max.   :33.90   Max.   :8.000   Max.   :472.0   Max.   :335.0  
      drat             wt             qsec             vs        
 Min.   :2.760   Min.   :1.513   Min.   :14.50   Min.   :0.0000  
 1st Qu.:3.080   1st Qu.:2.581   1st Qu.:16.89   1st Qu.:0.0000  
 Median :3.695   Median :3.325   Median :17.71   Median :0.0000  
 Mean   :3.597   Mean   :3.217   Mean   :17.85   Mean   :0.4375  
 3rd Qu.:3.920   3rd Qu.:3.610   3rd Qu.:18.90   3rd Qu.:1.0000  
 Max.   :4.930   Max.   :5.424   Max.   :22.90   Max.   :1.0000  
       am              gear            carb      
 Min.   :0.0000   Min.   :3.000   Min.   :1.000  
 1st Qu.:0.0000   1st Qu.:3.000   1st Qu.:2.000  
 Median :0.0000   Median :4.000   Median :2.000  
 Mean   :0.4062   Mean   :3.688   Mean   :2.812  
 3rd Qu.:1.0000   3rd Qu.:4.000   3rd Qu.:4.000  
 Max.   :1.0000   Max.   :5.000   Max.   :8.000  

head(mtcars,2)

              mpg cyl disp  hp drat    wt  qsec vs am gear carb
Mazda RX4      21   6  160 110  3.9 2.620 16.46  0  1    4    4
Mazda RX4 Wag  21   6  160 110  3.9 2.875 17.02  0  1    4    4

The application is built using Shiny web framework from RStudio.

You can find the code @ GitHub repository

The whole source code is composed by two files:

• ui.R There are two main areas as a sidebar to select the features of the data mtcars and a central 3-tabs panel with multiple plots.
• server.R It uses reactive component of the Shiny framework to return all the 3 plots every time a single option is checked from the sidebar. Also, using the validate option, an error message will be displayed in the 3 tabs, if none of the features are selected.

From the sidebar a user can select one or more features of the mtcars data, excluding the mpg (that gets predicted). When one of the features is checked, the application will display the new generated plots. If none of the features is selected, instead an error message will be displayed.

The 3 tabs include the following plots:

• Linear Models shows the prediction of the linear model (black line) created by the selected features vs mpg ~ am (blue line - am is a good predictor on its own) vs mpg ~ . (red line).
• HatValues shows the hatvalues plot by car models for the selected features.
• Betas shows the df-beats plot by car models for the selected features.