Bar Charts

Bar Charts are used to display the distribution of a single categorical variable.

All of the plots below use tools from the ggplot2 and dplyr packages.

library(ggplot2)  # Loads the ggplot2 library
library(dplyr)  # Loads the dplyr library

Bar Chart

The code below uses the class variable in the mpg dataset to create a bar chart with blue bars, a title, an x-axis label, and a legend.

mpg %>% 
  ggplot( aes(x = class)) + 
    geom_bar(fill = "blue") + 
    labs(
      title = "Distribution of Automobile Classs", 
      x = "Automobile Class"
      ) + 
    theme_bw()

The bars can be displayed vertically by adding coord_flip() to the previously created plot.

mpg %>% 
  ggplot( aes(x = class)) + 
    geom_bar(fill = "blue") + 
    labs(
      title = "Distribution of Automobile Classs", 
      x = "Automobile Class"
      ) + 
    theme_bw() + 
    coord_flip()

Bar Chart with Relative Frequency

The code below produces a bar chart that has relative frequency instead of frequency on the y axis.

mpg %>% 
  ggplot( aes(x = class, y = ..prop.., group = 1)) + 
    geom_bar(fill = "blue") + 
    labs(
      title = "Distribution of Automobile Classs", 
      x = "Automobile Class"
      ) + 
    theme_bw()

Stacked Bar Chart

mpg %>% 
  ggplot( aes(x = "", fill = class)) + 
    geom_bar(color = "white") + 
    labs(
      title = "Distribution of Automobile Classs", 
      x = ""
      ) + 
    theme_bw()

Side-By-Side Bar Chart

Side-by-side bar charts are used to display the relationship between a categorical explanitory variable and a categorical response variable.

The code below creates side-by-side bar chars of drive train type for all of the automobile class.

mpg %>% 
  ggplot( aes(x = class, fill = drv)) + 
    geom_bar(position = "dodge") + 
    labs(
      title = "Distribution of Automobile Classs", 
      x = "Automobile Class", 
      fill = "Drive Train"
      ) + 
    theme_bw()

mpg %>% 
  ggplot( aes(x = "", fill = drv)) + 
    geom_bar(position = "dodge") + 
    labs(
      title = "Distribution of Automobile Classs", 
      x = "Automobile Class", 
      fill = "Drive Train"
      ) + 
  facet_grid(. ~ class)

Stacked Bar Charts

The code below creates stacked bar charts for the drive train type of all of the automobile classs

mpg %>% 
  ggplot( aes(x = class, fill = drv)) + 
    geom_bar() + 
    labs(
      title = "Distribution of Automobile Classs", 
      x = "Automobile Class", 
      fill = "Drive Train"
      ) + 
    theme_bw()

Stacked Bar Chart with Relative Frequencies

The code below creates stacked bar charts with relative frequencies for the drive train type of all of the automobile classs A mosaic plot should be used when there are an unequal number of cars within each class of cylinder.

mpg %>% 
  ggplot( aes(x = class, fill = drv)) + 
    geom_bar(position = "fill") + 
    labs(
      title = "Distribution of Automobile Classs", 
      x = "Automobile Class", 
      fill = "Drive Train"
      ) + 
    theme_bw()

Mathematicss, Computer Science, and Statistics Department Gustavus Adolphus College