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.
geom_dotplot(mapping = NULL, data = NULL, position = "identity", ..., binwidth = NULL, binaxis = "x", method = "dotdensity", binpositions = "bygroup", stackdir = "up", stackratio = 1, dotsize = 1, stackgroups = FALSE, origin = NULL, right = TRUE, width = 0.9, drop = FALSE, na.rm = FALSE, show.legend = NA, inherit.aes = TRUE)
Set of aesthetic mappings created by
aes_. If specified and
inherit.aes = TRUE (the
default), it is combined with the default mapping at the top level of the
plot. You must supply
mapping if there is no plot mapping.
The data to be displayed in this layer. There are three options:
NULL, the default, the data is inherited from the plot
data as specified in the call to
data.frame, or other object, will override the plot
data. All objects will be fortified to produce a data frame. See
fortify for which variables will be created.
function will be called with a single argument,
the plot data. The return value must be a
will be used as the layer data.
Position adjustment, either as a string, or the result of a call to a position adjustment function.
other arguments passed on to
layer. These are
often aesthetics, used to set an aesthetic to a fixed value, like
color = "red" or
size = 3. They may also be parameters
to the paired geom/stat.
method is "dotdensity", this specifies maximum bin
method is "histodot", this specifies bin width.
Defaults to 1/30 of the range of the data
The axis to bin along, "x" (default) or "y"
"dotdensity" (default) for dot-density binning, or "histodot" for fixed bin widths (like stat_bin)
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.
which direction to stack the dots. "up" (default), "down", "center", "centerwhole" (centered, but with dots aligned)
how close to stack the dots. Default is 1, where dots just just touch. Use smaller values for closer, overlapping dots.
The diameter of the dots relative to
binwidth, default 1.
should dots be stacked across groups? This has the effect
position = "stack" should have, but can't (because this geom has
some odd properties).
method is "histodot", origin of first bin
method is "histodot", should intervals be closed
on the right (a, b], or not [a, b)
binaxis is "y", the spacing of the dot stacks
If TRUE, remove all bins with zero counts
FALSE, the default, missing values are removed with
a warning. If
TRUE, missing values are silently removed.
logical. Should this layer be included in the legends?
NA, the default, includes if any aesthetics are mapped.
FALSE never includes, and
TRUE always includes.
FALSE, overrides the default aesthetics,
rather than combining with them. This is most useful for helper functions
that define both data and aesthetics and shouldn't inherit behaviour from
the default plot specification, e.g.
There are two basic approaches: dot-density and histodot.
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
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.
geom_dotplot understands the following aesthetics (required aesthetics are in bold):
center of each bin, if binaxis is "x"
center of each bin, if binaxis is "x"
max width of each bin if method is "dotdensity"; width of each bin if method is "histodot"
number of points in bin
count, scaled to maximum of 1
density of points in bin, scaled to integrate to 1, if method is "histodot"
density, scaled to maximum of 1, if method is "histodot"
Wilkinson, L. (1999) Dot plots. The American Statistician, 53(3), 276-281.
#># 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")# 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)# Overlap dots vertically ggplot(mtcars, aes(x = mpg)) + geom_dotplot(binwidth = 1.5, stackratio = .7)# 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 = "centerwhole")#>ggplot(mtcars, aes(x = factor(vs), fill = factor(cyl), y = mpg)) + geom_dotplot(binaxis = "y", stackdir = "center", position = "dodge")#># 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")#># 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")