Dot plots: geom_dotplot

Mix.install([
  {:giggly, path: Path.join(__DIR__, "..")},
  {:kino, "~> 0.19"}
  ])

About this notebook

This notebook follows the examples on ggplot2's reference page for geom_dotplot(), in the order the page gives them. Each example shows ggplot2's code first and then Giggly's. An example Giggly cannot draw yet keeps its ggplot2 code and names what it is waiting for, so the page is also a list of what remains.

A dot plot shows how one column's values are spread: it bins them and stacks one dot for each row in a bin, each dot as wide as the bin. ggplot2 bins in one of two ways: by dot density, where the data and a largest bin width decide where the bins fall, or as a histogram does, with bins of one width at fixed places. It can bin along y instead of x, stack the dots up, down or about the centre, and stack several groups on one another. Giggly has no dot plots yet. The examples' data, R's mtcars, is in Giggly already, as Giggly.Datasets.mtcars/0.

A dot plot

ggplot(mtcars, aes(x = mpg)) +
  geom_dotplot()

With no binwidth, ggplot2 takes a thirtieth of the data's range as the widest a bin may be, and says so.

Not in Giggly yet: geom_dotplot().

The width of the bins

ggplot(mtcars, aes(x = mpg)) +
  geom_dotplot(binwidth = 1.5)

Not in Giggly yet: geom_dotplot() and its binwidth option.

Bins of one width

# Use fixed-width bins
ggplot(mtcars, aes(x = mpg)) +
  geom_dotplot(method="histodot", binwidth = 1.5)

method = "histodot" puts the bins at fixed places, all as wide as binwidth, as a histogram does, rather than letting the data decide where each one starts.

Not in Giggly yet: geom_dotplot() and its method and binwidth options.

Stacking about the centre

# Some other stacking methods
ggplot(mtcars, aes(x = mpg)) +
  geom_dotplot(binwidth = 1.5, stackdir = "center")

ggplot(mtcars, aes(x = mpg)) +
  geom_dotplot(binwidth = 1.5, stackdir = "centerwhole")

"center" stacks the dots out both ways from the middle rather than up from the axis; "centerwhole" does too, but keeps the dots of neighbouring stacks in line.

Not in Giggly yet: geom_dotplot() and its binwidth and stackdir options.

Hiding the y axis

# y axis isn't really meaningful, so hide it
ggplot(mtcars, aes(x = mpg)) + geom_dotplot(binwidth = 1.5) +
  scale_y_continuous(NULL, breaks = NULL)

The numbers on a dot plot's y axis count nothing, so the example removes the axis's title and breaks.

Not in Giggly yet: geom_dotplot() and its binwidth option.

Overlapping dots

# Overlap dots vertically
ggplot(mtcars, aes(x = mpg)) +
  geom_dotplot(binwidth = 1.5, stackratio = .7)

Not in Giggly yet: geom_dotplot() and its binwidth and stackratio options.

Larger dots

# Expand dot diameter
ggplot(mtcars, aes(x = mpg)) +
  geom_dotplot(binwidth = 1.5, dotsize = 1.25)

Not in Giggly yet: geom_dotplot() and its binwidth and dotsize options.

A dot's fill and border

# Change dot fill colour, stroke width
ggplot(mtcars, aes(x = mpg)) +
  geom_dotplot(binwidth = 1.5, fill = "white", stroke = 2)

Not in Giggly yet: geom_dotplot() and its binwidth option.

Binning along y

# Examples with stacking along y axis instead of x
ggplot(mtcars, aes(x = 1, y = mpg)) +
  geom_dotplot(binaxis = "y", stackdir = "center")

ggplot(mtcars, aes(x = factor(cyl), y = mpg)) +
  geom_dotplot(binaxis = "y", stackdir = "center")

ggplot(mtcars, aes(x = factor(cyl), y = mpg)) +
  geom_dotplot(binaxis = "y", stackdir = "centerwhole")

binaxis = "y" bins mpg up the y axis and stacks the dots sideways, one stack for each x.

Not in Giggly yet: geom_dotplot() and its binaxis and stackdir options.

Dodging groups

ggplot(mtcars, aes(x = factor(vs), fill = factor(cyl), y = mpg)) +
  geom_dotplot(binaxis = "y", stackdir = "center", position = "dodge")

Not in Giggly yet: geom_dotplot() and its binaxis and stackdir options.

Aligning the bins of groups

# binpositions="all" ensures that the bins are aligned between groups
ggplot(mtcars, aes(x = factor(am), y = mpg)) +
  geom_dotplot(binaxis = "y", stackdir = "center", binpositions="all")

Not in Giggly yet: geom_dotplot() and its binaxis, stackdir and binpositions options.

Stacking groups

# Stacking multiple groups, with different fill
ggplot(mtcars, aes(x = mpg, fill = factor(cyl))) +
  geom_dotplot(stackgroups = TRUE, binwidth = 1, binpositions = "all")

ggplot(mtcars, aes(x = mpg, fill = factor(cyl))) +
  geom_dotplot(stackgroups = TRUE, binwidth = 1, method = "histodot")

ggplot(mtcars, aes(x = 1, y = mpg, fill = factor(cyl))) +
  geom_dotplot(binaxis = "y", stackgroups = TRUE, binwidth = 1, method = "histodot")

stackgroups = TRUE stacks each group's dots on the dots of the groups before it, as position = "stack" would if a dot plot could use it.

Not in Giggly yet: geom_dotplot() and its stackgroups, binwidth, binpositions, method and binaxis options.