Dot plot

Usage

geom_dotplot(mapping = NULL, data = NULL, stat = "bindot", position = "identity", 
  na.rm = FALSE, binwidth = NULL, binaxis = "x", method = "dotdensity", binpositions = "bygroup", 
      stackdir = "up", stackratio = 1, dotsize = 1, stackgroups = FALSE, ...)

Arguments

binaxis
which axis to bin along "x" (default) or "y"
method
"dotdensity" (default) for dot-density binning, or "histodot" for fixed bin widths (like stat_bin)
binwidth
When method is "dotdensity", this specifies maximum bin width. When method is "histodot", this specifies bin width. Defaults to 1/30 of the range of the data
binpositions
When method is "dotdensity", "bygroup" (default) determines positions of the bins for each group separately. "all" determines positions of the bins with all the data taken together; this is used for aligning dot stacks across multiple groups.
stackdir
which direction to stack the dots. "up" (default), "down", "center", "centerwhole" (centered, but with dots aligned)
stackratio
how close to stack the dots. Default is 1, where dots just just touch. Use smaller values for closer, overlapping dots.
dotsize
The diameter of the dots relative to binwidth, default 1.
stackgroups
should dots be stacked across groups? This has the effect that position = "stack" should have, but can't (because this geom has some odd properties).
mapping
The aesthetic mapping, usually constructed with aes or aes_string. Only needs to be set at the layer level if you are overriding the plot defaults.
data
A layer specific dataset - only needed if you want to override the plot defaults.
stat
The statistical transformation to use on the data for this layer.
position
The position adjustment to use for overlappling points on this layer
na.rm
If FALSE (the default), removes missing values with a warning. If TRUE silently removes missing values.
...
other arguments passed on to layer. This can include aesthetics whose values you want to set, not map. See layer for more details.

Description

In a dot plot, the width of a dot corresponds to the bin width (or maximum width, depending on the binning algorithm), and dots are stacked, with each dot representing one observation.

Details

With dot-density binning, the bin positions are determined by the data and binwidth, which is the maximum width of each bin. See Wilkinson (1999) for details on the dot-density binning algorithm.

With histodot binning, the bins have fixed positions and fixed widths, much like a histogram.

When binning along the x axis and stacking along the y axis, the numbers on y axis are not meaningful, due to technical limitations of ggplot2. You can hide the y axis, as in one of the examples, or manually scale it to match the number of dots.

Aesthetics

geom_dotplot understands the following aesthetics (required aesthetics are in bold):

  • x
  • y
  • alpha
  • colour
  • fill

References

Wilkinson, L. (1999) Dot plots. The American Statistician, 53(3), 276-281.

Examples

ggplot(mtcars, aes(x = mpg)) + geom_dotplot()
stat_bindot: binwidth defaulted to range/30. Use 'binwidth = x' to adjust this.

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

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

# 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")

# y axis isn't really meaningful, so hide it ggplot(mtcars, aes(x = mpg)) + geom_dotplot(binwidth = 1.5) + scale_y_continuous(name = "", breaks = NA)
Warning message: breaks = NA is deprecated. Please use breaks = NULL to remove breaks in the scale. (Deprecated; last used in version 0.8.9)

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

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

# Examples with stacking along y axis instead of x ggplot(mtcars, aes(x = 1, y = mpg)) + geom_dotplot(binaxis = "y", stackdir = "center")
stat_bindot: binwidth defaulted to range/30. Use 'binwidth = x' to adjust this.

ggplot(mtcars, aes(x = factor(cyl), y = mpg)) + geom_dotplot(binaxis = "y", stackdir = "center")
stat_bindot: binwidth defaulted to range/30. Use 'binwidth = x' to adjust this.

ggplot(mtcars, aes(x = factor(cyl), y = mpg)) + geom_dotplot(binaxis = "y", stackdir = "centerwhole")
stat_bindot: binwidth defaulted to range/30. Use 'binwidth = x' to adjust this.

ggplot(mtcars, aes(x = factor(vs), fill = factor(cyl), y = mpg)) + geom_dotplot(binaxis = "y", stackdir = "center", position = "dodge")
stat_bindot: binwidth defaulted to range/30. Use 'binwidth = x' to adjust this.

# 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")
stat_bindot: binwidth defaulted to range/30. Use 'binwidth = x' to adjust this.

# 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")