Bar Plots

A bar plot creates a bar for each level of a factor variable. An easy way to think about this is if you had a question with four possible answers, A, B, C, and D. A bar plot of the data would have a bar labeled A, and the height of the bar would be the number of times someone had answered A. Then there would be a bar labeled B, whose height was the number of times people had answered B. Etcetera.

Lets look at a concrete example. If you use the plot() function on categorical data,


you will get a bar plot that looks like this:

Plot 1

Each bar represents how many times each of those categories appeared in the data set. So, bike lane appeared 5 times (there were five rows in the labike.csv dataset that said bike lane), bike path and bike route each appeared a little more than 5 times, and none appeared 20 times. This lets you see the distribution of responses.

Another way you could have made a barplot is using the barplot() function:


Bar plot 1

This plot shows us that both Male and Female appeared about 7000 times. Since these data came from a random survey, we would expect to see a 50/50 split between genders, so this makes sense.