# Bar Graph

A bar graph of a qualitative data sample consists of vertical parallel bars that shows the frequency distribution graphically.

#### Example

In the data set painters, the bar graph of the School variable is a collection of vertical bars showing the number of painters in each school.

#### Problem

Find the bar graph of the painter schools in the data set painters.

#### Solution

We first apply the table function to compute the frequency distribution of the School variable.

> library(MASS)                 # load the MASS package
> school = painters\$School      # the painter schools
> school.freq = table(school)   # apply the table function

Then we apply the barplot function to produce its bar graph.

> barplot(school.freq)         # apply the barplot function

The bar graph of the school variable is:

#### Enhanced Solution

To colorize the bar graph, we select a color palette and set it in the col argument of barplot.

> colors = c("red", "yellow", "green", "violet",
+   "orange", "blue", "pink", "cyan")
> barplot(school.freq,         # apply the barplot function
+   col=colors)                # set the color palette

#### Exercise

Find the bar graph of the composition scores in painters.