How to Create a Bar Chart with R

Should you want to create a bar chart while using R, the following excerpt below from the O'Reilly publication 25 Recipes for Getting Started with R will show you how.

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Use the barplot function. The first argument is a vector of bar heights:

> barplot(c(height1, height2, height3))

The barplot function produces a simple bar chart. It assumes that the heights of your bars are conveniently stored in a vector. That is not always the case, however. Often, you have a vector of numeric data and a parallel factor that groups the data, and you want to produce a bar chart of the group means or the group totals. For example, the airquality dataset contains a numeric Temp column and a Month column. We can create a bar chart of the mean temperature by month in two steps. First, we compute the means:

> heights <- tapply(airquality$Temp, airquality$Month, mean)

That gives the heights of the bars, from which we create the bar chart:

> barplot(heights)

The result is shown in the lefthand panel of Figure 1-4. The result is pretty bland, as you can see, so it’s common to add some simple adornments: a title, labels for the bars, and a label for the y-axis:

> barplot(heights,
+         main="Mean Temp. by Month",
+         names.arg=c("May", "Jun", "Jul", "Aug", "Sep"),
+         ylab="Temp (deg. F)")

The righthand panel of Figure 1-4 shows the improved bar chart.

The barchart function in the lattice package is another way to produce a bar chart.