Visualizing a Single Distribution

• Histogram

• Density plot

• Cumulative density

• Quantile-Quantile plot

Cumulative density and Quantile-Quantile plot are hard to interpret.

Visualizing multiple distributions

Histogram - Binwidth

Histogram-Binwidth (.1)

Narrow

Histogram-Binwidth (2)

Wide

Add a rug

Histogram - Example

ggplot(iris, aes(x = Sepal.Length)) +
geom_histogram(binwidth = .2, fill = "orange", colour = "black") +
geom_rug() +
facet_wrap(~ Species)

Boxplot

Medium to Large N

Boxplot - Example

ggplot(iris, aes(y = Sepal.Length, x = Species)) +
geom_boxplot()

Add notches

“Notches are used to compare groups; if the notches of two boxes do not overlap, this is strong evidence that the medians differ.” (Chambers et al., 1983, p. 62)

Boxplot with notch - Example

ggplot(iris, aes(y = Sepal.Length, x = Species)) +
geom_boxplot(notch = T)

Your turn: Perform ANOVA.

Add summary statistics

Green: Mean

Boxplot with summary - Example

ggplot(iris, aes(y = Sepal.Length, x = Species)) +
geom_boxplot() +
  stat_summary(fun.y=mean)

Boxplot with summary - Example

Your turn: Add min, max, Q1, Q2, Q3

Stripchart

Small to Medium

Stripchart - Example

Boxplot using geom_dotplot

Small to Medium

Boxplot using geom_dotplot - Example

ggplot(iris, aes(x = Species, 
                 y = Sepal.Length)) +
geom_dotplot(stackdir = "center",
binaxis = "y", binwidth = .1,
binpositions = "all",
stackratio = 1.5,
fill = "#7570b3", colour = "#7570b3")

ggplot(iris, aes(x = Species, 
                 y = Sepal.Length)) +
geom_dotplot(stackdir = "center",
binaxis = "y", binwidth = .05,
binpositions = "all",
stackratio = 1.5,
fill = "#7570b3", colour = "#7570b3")

Bee swarm

Beeswarm

Boxplot with dot points

Boxplot with dot points - Example

ggplot(iris, aes(y = Sepal.Length, x = Species)) +
geom_boxplot(outlier.shape = NA) +
geom_dotplot(binaxis = 'y',
stackdir = 'center', fill = "#7570b3", colour = "#7570b3", 
binwidth = .05)

Boxplot with dot points

Boxplot with dot points (geom="jitter")

ggplot(iris, aes(y = Sepal.Length, x = Species)) +
geom_boxplot(outlier.shape = NA, width = .5) +
geom_jitter(fill = "#7570b3", colour = "#7570b3",
position = position_jitter(height = 0, width = .1), alpha = .5)

Density plots

Medium to large n

Density plot

Density plots - Example

ggplot(iris, aes(x = Sepal.Length)) + 
  geom_density(fill = "#7570b3") + 
  facet_wrap(~ Species)

ggplot(iris, aes(x = Sepal.Length, 
                 fill=Species)) + 
  geom_density(alpha=0.5)

Density plot and Histogram

Density plot and Histogram - Example

ggplot(iris, aes(x = Sepal.Length)) +
geom_histogram(aes(y = ..density..),
binwidth = .5, colour = "black",
fill = "white") +
geom_density(alpha = .5, fill = "#7570b3") +
facet_wrap(~ Species)

Violin plot

Violin plot - Example

ggplot(iris, aes(x = Species, y = Sepal.Length)) +
geom_violin(color = NA,
fill = "#7570b3", na.rm = TRUE,
scale = "count")

Violin plot + Boxplot

Violin plot + Boxplot

ggplot(iris, aes(x = Species, y = Sepal.Length)) +
geom_boxplot(outlier.size = 2, colour="#7570b3", width=.1) +
geom_violin(alpha = .2, fill = "#7570b3")

Ridgeline plots

Ridgeline plots - Example

library(ggridges)
ggplot(iris, aes(x = Sepal.Length, y = Species)) +
geom_density_ridges(scale = 0.9,
fill = "#7570b3", alpha = .5)

Raincloud plot

Raincloud plots - Example

library(ggridges)
ggplot(iris, aes(x = Sepal.Length, y = Species)) +
geom_density_ridges(scale = 0.9,
                    position= "raincloud",
                    jittered_points = TRUE,
fill = "#7570b3", alpha = .5)