# Bar Plots

Create barplots with the **barplot(***height***)** function, where *height* is a vector or matrix. If **height is a vector**, the values determine the heights of the bars in the plot. If **height is a matrix** and the option **beside=FALSE** then each bar of the plot corresponds to a column of height, with the values in the column giving the heights of stacked “sub-bars”. If **height is a matrix** and **beside=TRUE**, then the values in each column are juxtaposed rather than stacked. Include option **names.arg=(***character vector***) **to label the bars. The option **horiz=TRUE** to createa a horizontal barplot.

## Simple Bar Plot

`# Simple Bar Plot `

counts <- table(mtcars$gear)

barplot(counts, main="Car Distribution",

xlab="Number of Gears")

`# Simple Horizontal Bar Plot with Added Labels `

counts <- table(mtcars$gear)

barplot(counts, main="Car Distribution", horiz=TRUE,

names.arg=c("3 Gears", "4 Gears", "5 Gears"))

## Stacked Bar Plot

`# Stacked Bar Plot with Colors and Legend`

counts <- table(mtcars$vs, mtcars$gear)

barplot(counts, main="Car Distribution by Gears and VS",

xlab="Number of Gears", col=c("darkblue","red"),

legend = rownames(counts))

## Grouped Bar Plot

`# Grouped Bar Plot`

counts <- table(mtcars$vs, mtcars$gear)

barplot(counts, main="Car Distribution by Gears and VS",

xlab="Number of Gears", col=c("darkblue","red"),

legend = rownames(counts), beside=TRUE)

## Notes

Bar plots need not be based on counts or frequencies. You can create bar plots that represent means, medians, standard deviations, etc. Use the **aggregate( ) **function and pass the results to the **barplot( )** function.

By default, the categorical axis line is suppressed. Include the option **axis.lty=1** to draw it.

With many bars, bar labels may start to overlap. You can decrease the font size using the **cex.names =** option. Values smaller than one will shrink the size of the label. Additionally, you can use graphical parameters such as the following to help text spacing:

`# Fitting Labels `

par(las=2) # make label text perpendicular to axis

par(mar=c(5,8,4,2)) # increase y-axis margin.

counts <- table(mtcars$gear)

barplot(counts, main="Car Distribution", horiz=TRUE, names.arg=c("3 Gears", "4 Gears", "5 Gears"), cex.names=0.8)

## To practice

Try the bar plot exercises in this course on data visualization in R.