A bar chart is the simplest chart that displays the frequency of a categorical variable or the summary statistics of a numeric variable over the category of other variables. In this recipe, we will learn how we can produce a bar chart using the ggplot2
library.
Let's call the ggplotdata
dataset that was created in the preceding section. We intend to produce a bar chart that will represent the mean of a numeric variable on the y axis over the category of the economic status variable on the x-axis. So, we need to prepare the summarized dataset as follows:
library(plyr) bardata <- ddply(ggplotdata,.(econ_status),summarize,meandisA=mean(disA), meandisB=mean(disB),meandisC=mean(disC),meadisD=mean(disD))
The description of the most important components of the preceding function is as follows:
The
ddply()
function takes the data frame as the input and produces the output in the data frame as well. In the function name, the firstd
signifies the input data frame and...