Exercise

# Using the symbols() function to display relations between more than two variables

The scatterplot allows us to see how one numerical variable changes with the values of a second numerical variable. The `symbols()`

function allows us to extend scatterplots to show the influence of other variables.

This function is called with the variables `x`

and `y`

that define a scatterplot, along with another argument that specifies one of several possible shapes. Here, you are asked to use the `circles`

argument to create a *bubbleplot* where each data point is represented by a circle whose radius depends on the third variable specified by the value of this argument.

Instructions

**100 XP**

The `Cars93`

data frame from the `MASS`

package is already available in your workspace.

- Use the
`symbols()`

function with its default settings and the appropriate arguments to create a bubble plot of`MPG.city`

versus`Horsepower`

from the`Cars93`

data frame, with the bubble area by the`Price`

variable. Note that this means the bubble radius should be proportional to the square root (`sqrt()`

) of`Price`

. - Re-create the first plot, but with the optional argument
`inches`

set to 0.1.