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Tufte's box plot

Source: R/geom-tufteboxplot.R
geom_tufteboxplot.Rd

Edward Tufte's revisions of the box plot as described in The Visual Display of Quantitative Information. This function provides several box plot variants:

  • A point indicating the median, a gap indicating the interquartile range, and lines for whiskers.

  • An offset line indicating the interquartile range and a gap indicating the median.

  • A line indicating the interquartile range, a gap indicating the median, and points indicating the minimum and maximum values.

  • A wide line indicating the interquartile range, a gap indicating the median, and lines indicating the minimum and maximum.

Usage

geom_tufteboxplot(
  mapping = NULL,
  data = NULL,
  stat = "fivenumber",
  position = "dodge",
  outlier.colour = "black",
  outlier.shape = 19,
  outlier.size = 1.5,
  outlier.stroke = 0.5,
  voffset = 0.01,
  hoffset = 0.005,
  na.rm = FALSE,
  show.legend = NA,
  inherit.aes = TRUE,
  median.type = "point",
  whisker.type = "line",
  ...
)

Arguments

mapping

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.

data

The data to be displayed in this layer. There are three options:

If NULL, the default, the data is inherited from the plot data as specified in the call to ggplot().

A 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.

A function will be called with a single argument, the plot data. The return value must be a data.frame, and will be used as the layer data. A function can be created from a formula (e.g. ~ head(.x, 10)).

stat

The statistical transformation to use on the data for this layer, as a string. The default (stat = 'fivenumber') calls stat_fivenumber() and produces whiskers that extend from the interquartile range to the extremes of the data; specifying ggplot2::stat_boxplot() will produce a more traditional boxplot with whiskers extending to the most extreme points that are < 1.5 IQR away from the hinges (i.e., the first and third quartiles).

position

A position adjustment to use on the data for this layer. This can be used in various ways, including to prevent overplotting and improving the display. The position argument accepts the following:

  • The result of calling a position function, such as position_jitter(). This method allows for passing extra arguments to the position.

  • A string naming the position adjustment. To give the position as a string, strip the function name of the position_ prefix. For example, to use position_jitter(), give the position as "jitter".

  • For more information and other ways to specify the position, see the layer position documentation.

outlier.colour

Color of outlying points.

outlier.shape

Shape of outlying points.

outlier.size

Size of outlying points.

outlier.stroke

Stroke width of outlying points.

voffset

Controls the size of the gap in the line representing the median when median.type = "line". This is a fraction of the range of y.

hoffset

Controls how much the interquartile line is offset from the whiskers when median.type = "line". This is a fraction of the range of x.

na.rm

If FALSE, the default, missing values are removed with a warning. If TRUE, missing values are silently removed.

show.legend

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. It can also be a named logical vector to finely select the aesthetics to display. To include legend keys for all levels, even when no data exists, use TRUE. If NA, all levels are shown in legend, but unobserved levels are omitted.

inherit.aes

If 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. annotation_borders().

median.type

How to represent the median, one of:

  • "point", the default: the median is a point, and the interquartile range is a gap in the line.

  • "line": the interquartile range is a line, possibly offset, and the median is a gap in the line.

whisker.type

How to represent the whiskers, one of:

  • "line", the default: whiskers are lines.

  • "point": whiskers are points at ymin and ymax.

...

Other arguments passed on to layer()'s params argument. These arguments broadly fall into one of 4 categories below. Notably, further arguments to the position argument, or aesthetics that are required can not be passed through .... Unknown arguments that are not part of the 4 categories below are ignored.

  • Static aesthetics that are not mapped to a scale, but are at a fixed value and apply to the layer as a whole. For example, colour = "red" or linewidth = 3. The geom's documentation has an Aesthetics section that lists the available options. The 'required' aesthetics cannot be passed on to the params. Please note that while passing unmapped aesthetics as vectors is technically possible, the order and required length is not guaranteed to be parallel to the input data.

  • When constructing a layer using a stat_*() function, the ... argument can be used to pass on parameters to the geom part of the layer. An example of this is stat_density(geom = "area", outline.type = "both"). The geom's documentation lists which parameters it can accept.

  • Inversely, when constructing a layer using a geom_*() function, the ... argument can be used to pass on parameters to the stat part of the layer. An example of this is geom_area(stat = "density", adjust = 0.5). The stat's documentation lists which parameters it can accept.

  • The key_glyph argument of layer() may also be passed on through .... This can be one of the functions described as key glyphs, to change the display of the layer in the legend.

Value

A ggplot2 layer.

Aesthetics

  • x (required)

  • y (required)

  • colour

  • size

  • linewidth

  • linetype

  • shape

  • fill

  • alpha

References

Tufte, Edward R. (2001) The Visual Display of Quantitative Information, Chapter 6.

McGill, R., Tukey, J. W. and Larsen, W. A. (1978) Variations of box plots. The American Statistician 32, 12-16.

See also

ggplot2::geom_boxplot()

Other geom tufte: geom_rangeframe()

Other tufte: extended_range_breaks_(), geom_rangeframe(), theme_tufte()

Examples

library("ggplot2")

p <- ggplot(mtcars, aes(factor(cyl), mpg))
# with a point for the median and lines for whiskers
p + geom_tufteboxplot()

# with a line for the interquartile range and points for whiskers
p + geom_tufteboxplot(median.type = "line", whisker.type = "point", hoffset = 0)

# with a wide line for the interquartile range and lines for whiskers.
# `width` scales the median line but is also the box width, so use
# position = "identity" to stop position_dodge() warning about overlaps.
p + geom_tufteboxplot(median.type = "line", hoffset = 0, width = 3, position = "identity")

# with an offset line for the interquartile range and lines for whiskers
p + geom_tufteboxplot(median.type = "line")

# combined with theme_tufte
p + geom_tufteboxplot() + theme_tufte() + theme(axis.ticks.x = element_blank())

# traditional boxplot with whiskers only out to 1.5 IQR, outlier points
p + geom_tufteboxplot(stat = "boxplot", outlier.shape = 5)