barplot

Bar graphs or bar charts are created using barplot, and are frequency comparisons for categorical data (rather than numeric occurrences of a single variable as with histograms). Heights of bars are proportional to the frequency of occurrence of each category.

Use a bar graph when you want to compare the incidence of different but similar things. Survival of different mammals on a flooded island, on the number of paper subscriptions in several city neighborhoods.

Bar graphs can be single bars per category. They can also be "doubled-up" -- two or more bars in the same category turning on a split in the data. An example might be paper subscriptions in city neighborhoods, split by gender. Bar graphs may also be "stacked," with each bar divided into a number of differently colored segments representing random characteristics (that is, characteristics which may not appear in every bar in the chart). For example, paper subscriptions per neighborhood, with segments for morning, evening, and Sunday only subscriptions. In some neighborhoods there may be no Sunday only subscriptions, while in another neighborhood, everybody gets the morning edition.

R Example

This example plots the number of states which exist in the four main regions of the U.S.

barplot(table(state.region))

Number of States in Four U.S. Regions