• data visualization package for R created by Hadley Wickham in 2005
• implementation of Leland Wilkinson's Grammar of Graphics: break up graphs into semantic components such as scales and layers
• provides defaults for web and print display of common scales
• high degree of modularity

ggplot2 allows you to:

1. Think about your graphics via layers
2. Apply an organized grammar of graphics for visualization development
3. …

What you'll see here is just the beginning! See more at http://docs.ggplot2.org/current/

Syntax for ggplot2 visualizations will look like:

library(ggplot2)

ggplot(data = mpg, aes(x = displ, y = hwy)) +
        geom_point(aes(color = class)) +
        xlab("Engine Displacement (liters)") +
        ylab("Highway Mileage") +
        ggtitle("Fuel Economy vs. Engine Displacement") +
        theme_bw()

Load these packages to follow along with this tutorial

library(ggplot2)
library(readxl)
library(dplyr)
library(gridExtra)

Import the following data sets from the data folder

supermarket <- read_excel("../data/Supermarket-Transactions.xlsx", sheet = "Data")
facebook <- read.delim("../data/facebook.tsv")
reddit <- read.csv("../data/reddit.csv")
race <- read.csv("../data/race-comparison.csv")

ggplot(data = supermarket)
ggplot(data = supermarket, aes(x = `Purchase Date`, y = Revenue))

To display the data we need to tell ggplot what to draw

Check out all the available geoms at docs.ggplot2.org/current

ggplot(data = supermarket, aes(x = Revenue)) +
        geom_histogram()

ggplot(data = supermarket, aes(x = Revenue)) +
        geom_freqpoly()

ggplot(data = supermarket, aes(x = Revenue)) +
        geom_density()

ggplot(data = supermarket, aes(x = Revenue)) +
        geom_histogram(bins = 100, color = "grey40", fill = "white")

ggplot(data = supermarket, aes(x = Revenue)) +
        geom_freqpoly(bins = 100, color = "blue")

ggplot(data = supermarket, aes(x = Revenue)) +
        geom_density(fill = "red", alpha = .5)

ggplot(data = supermarket, aes(x = `Product Family`)) +
        geom_bar()

summary <- supermarket %>%
        group_by(`Product Family`) %>%
        tally()

ggplot(data = summary, aes(x = `Product Family`, y = n)) +
        geom_bar(stat = "identity")

ggplot(data = supermarket, aes(x = `Product Family`)) +
        geom_bar(fill = "dodgerblue", color = "grey40")

ggplot(data = supermarket, aes(x = `Product Family`)) +
        geom_bar(fill = "dodgerblue", color = "grey40", width = .75)

ggplot(data = supermarket, aes(x = `Product Family`)) +
        geom_bar(fill = "dodgerblue", color = "grey40", width = .99)

ggplot(supermarket, aes(`Purchase Date`, Revenue)) +
        geom_point()

ggplot(supermarket, aes(`Purchase Date`, Revenue)) +
        geom_point(colour = "blue", size = 1, shape = 5)

ggplot(supermarket, aes(`Purchase Date`, Revenue)) +
        geom_point(colour = "blue", alpha = .25)

ggplot(supermarket, aes(factor(`Units Sold`), Revenue)) +
        geom_point()

ggplot(supermarket, aes(factor(`Units Sold`), Revenue)) +
        geom_jitter(size = 1)

ggplot(supermarket, aes(factor(`Units Sold`), Revenue)) +
        geom_jitter(size = 1, alpha = .1)

sales_by_date <- supermarket %>%
        group_by(`Purchase Date`) %>%
        summarise(Revenue = sum(Revenue, na.rm = TRUE))

ggplot(sales_by_date, aes(`Purchase Date`, Revenue)) +
        geom_line()

sales_plot <- ggplot(sales_by_date, aes(`Purchase Date`, Revenue)) +
        geom_line()

sales_plot + geom_smooth(span = .1)

sales_plot + geom_smooth(span = .9, se = FALSE)

sales_plot + geom_smooth(method = "lm", se = FALSE)

ggplot(supermarket, aes(factor(Children), Revenue)) +
        geom_boxplot()

ggplot(supermarket, aes(factor(Children), Revenue)) +
        geom_boxplot(notch = TRUE, fill = "blue", alpha = .25)

ggplot(supermarket, aes(factor(Children), Revenue)) +
        geom_boxplot(outlier.color = "red", outlier.shape = 1)

Useful for smaller data sets like mpg

ggplot(mpg, aes(class, hwy)) +
        geom_boxplot()

ggplot(mpg, aes(class, hwy)) +
        geom_boxplot() +
        geom_jitter(width = .2, alpha = .5)

ggplot(mpg, aes(class, hwy)) +
        geom_violin()

Bar charts can have a y-axis different than just counts

ggplot(supermarket, aes(x = `Product Family`)) +
        geom_bar()

prod_revenue <- supermarket %>%
        group_by(`Product Family`) %>%
        summarise(Revenue = sum(Revenue, na.rm = TRUE))

ggplot(prod_revenue, aes(x = `Product Family`, y = Revenue)) +
        geom_bar(stat = "identity")

ggplot(supermarket, aes(Revenue, color = `Product Family`)) +
        geom_freqpoly()

ggplot(data = supermarket, aes(`Product Family`, fill = Gender)) +
        geom_bar(position = "dodge")

ggplot(supermarket, aes(`Purchase Date`, Revenue, color = Country)) +
        geom_point()

prod_revenue <- supermarket %>% group_by(`Purchase Date`, `Product Family`) %>%
        summarise(Revenue = sum(Revenue, na.rm = TRUE))
ggplot(prod_revenue, aes(`Purchase Date`, Revenue, color = `Product Family`)) +
  geom_line(alpha = .2) +
  scale_color_manual(values = c("#4f81bd", "#8cc841", "#c0504d")) +
        geom_smooth(se = FALSE, span = .1)

ggplot(prod_revenue, aes(`Purchase Date`, Revenue)) +
        geom_line(alpha = .2) +
        geom_smooth(se = FALSE, span = .1) +
        facet_wrap(~ `Product Family`)

ggplot(prod_revenue, aes(`Purchase Date`, Revenue)) +
        geom_blank() +
        facet_grid(.~ `Product Family`)

ggplot(prod_revenue, aes(`Purchase Date`, Revenue)) +
        geom_blank() +
        facet_grid(`Product Family` ~.)

p <- ggplot(supermarket, aes(Revenue)) +
        geom_histogram(bins = 100, color = "grey40", fill = "white")

p + scale_x_continuous(name = "Revenue from Individual Transactions",
                       limits = c(10, 50),
                       breaks = seq(10, 50, by = 10),
                       labels = scales::dollar)

p + scale_x_log10(labels = scales::dollar)        

Shorthand option for controlling the axis limits: xlim, ylim, lim

p + xlim(25, 55)

p + ylim(0, 400)

p + lims(x = c(0, 100), y = c(0, 1000))

Alternative is to use coord_cartesian; you can also rotate plots with coord_flip

p + coord_cartesian(xlim = c(10, 50), ylim = c(0, 400))

p + coord_flip()

Shorthand option for labelling axes and legends: labs, xlab, ylab, ggtitle

ggplot(prod_revenue, aes(`Purchase Date`, Revenue, color = `Product Family`)) +
        geom_line(alpha = .2) +
        geom_smooth(se = FALSE, span = .1) +
        labs(x = "x-axis title", y = "y-axis title", color = "legend title", title = "Main title")

Legend features can be controlled with guides and positioning is controlled within theme

ggplot(supermarket, aes(`Purchase Date`, Revenue, color = Country)) +
        geom_point(alpha = .2) +
        guides(color = guide_legend(override.aes = list(alpha = 1), reverse = TRUE)) +
        theme(legend.position = "bottom")

ggplot(supermarket, aes(Revenue)) +
        geom_histogram(bins = 100, fill = "antiquewhite", color = "grey40") +
        scale_x_continuous(limits = c(0, 60), breaks = seq(0, 60, by = 10),
                           labels = scales::dollar) +
        ggtitle("Gross Revenue per Transaction")

ggplot(city_rev, aes(Revenue, City, color = Gender)) +
        geom_point() +
        scale_x_continuous(labels = scales::dollar,
                           limits = c(0, 10000),
                           breaks = seq(0, 10000, by = 2000)) +
        labs(x = NULL, y = NULL, title = "Total Revenue by Gender and Location") +
        theme_minimal()

Several theme options are available (even more in the ggthemes package)

p <- ggplot(supermarket, aes(Revenue)) +
        geom_histogram(bins = 100, fill = "antiquewhite", color = "grey40")

p + theme_classic()
p + theme_minimal()
p + theme_dark()

basic

## `geom_smooth()` using method = 'loess'

basic + theme_minimal() +
        theme(
                text = element_text(family = "Georgia"),
                plot.title = element_text(face = "bold", size = 16), 
                legend.position = "top",
                axis.ticks = element_line(colour = "grey70", size = 0.2),
                panel.grid.major.y = element_line(linetype = "dashed", color = "darkgray"),
                panel.grid.major.x = element_blank(),
                panel.grid.minor = element_blank()
        )