# Scatter with multiple group

Most of the time it becomes essential to have a plot with multiple categories, i.e. colour coding scatter plot according to gender or have two different regression line for each of them.

Lets scatter the same points that the post – has dealt with but this time the points are coloured according to Transmission system (automatic vs manual) of the cars. In this article, the same three packages – Base Graphics, Lattice Plot and ggPlot will be used.

### Using Lattice Graphics

#### The Plot

In this section Lattice and Lattice Extra packages should be installed using the command
install.packages("lattice")and
install.packages("latticeExtra"). Then the package should be loaded using
library()

#### Source Code

To install lattice and latticeExtra package, you can use install.packages() function. It should be loaded after installation with library() function.

### Using ggPlot2

#### The Plot

Creating a ggPlot graphics is possible with installation of ggplot2 package. This package can create beautiful and sophisticated plots with simple syntax.

#### Source Code

Installation of ggplot2 package,

### The linear model and the fitted function

Call:
lm(formula = mpg ~ disp + am, data = mtcars)

Residuals:
Min 1Q Median 3Q Max
-4.6382 -2.4751 -0.5631 2.2333 6.8386

Coefficients:
Estimate Std. Error t value Pr(>|t|)
(Intercept) 27.848081 1.834071 15.184 2.45e-15 ***
disp -0.036851 0.005782 -6.373 5.75e-07 ***
am1 1.833458 1.436100 1.277 0.212
---
Signif. codes: 0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1

Residual standard error: 3.218 on 29 degrees of freedom
Multiple R-squared: 0.7333, Adjusted R-squared: 0.7149
F-statistic: 39.87 on 2 and 29 DF, p-value: 4.749e-09

For Automatic Transmission:

$$\texttt{mpg}=27.85-0.04\texttt{disp}$$

For Manual Transmission:

$$\texttt{mpg}=27.85-(0.04+1.83)\texttt{disp} = 27.85-1.87\texttt{disp}$$