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A stepped outline of a population pyramid

Source: R/geom-pyramid-outline.R
geom_pyramid_outline.Rd

geom_pyramid_outline() traces the outer edge of a pyramid as a stepped line, without filling the bars. Drawn over geom_pyramid(), it compares two populations, such as two census years or a region and the whole country. It aggregates the data in the same way as geom_pyramid(), so it accepts individual records and aggregated data alike.

Usage

geom_pyramid_outline(
  mapping = NULL,
  data = NULL,
  stat = "pyramid",
  position = position_pyramid(stack = FALSE),
  ...,
  denominator = NULL,
  lineend = "butt",
  linejoin = "mitre",
  linemitre = 10,
  na.rm = FALSE,
  orientation = NA,
  show.legend = NA,
  inherit.aes = TRUE
)

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. The default, "pyramid", is stat_pyramid().

position

A position adjustment. The default mirrors the left side without stacking, as position_pyramid(stack = FALSE), so that one line per side follows the total. The outline follows the side set by coord_pyramid(left = ...).

...

Other arguments passed on to ggplot2::layer(), such as fixed aesthetics like colour = "black" or linewidth = 0.8.

denominator

NULL (the default) shows counts. "total" shows each bar as a proportion of all rows in the panel, and "side" as a proportion of the rows on its side.

lineend

Line end style (round, butt, square).

linejoin

Line join style (round, mitre, bevel).

linemitre

Line mitre limit (number greater than 1).

na.rm

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

orientation

The orientation of the layer. The default (NA) automatically determines the orientation from the aesthetic mapping. In the rare event that this fails it can be given explicitly by setting orientation to either "x" or "y". See the Orientation section for more detail.

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().

Value

A ggplot2 layer.

Details

Each side gets one line, and so does each subgroup that fill, colour, linetype, linewidth or alpha sets apart. The line starts at zero below the youngest age group, follows the value of each group across its whole band, and returns to zero above the oldest. It drops to zero across an age group with no data.

Aesthetics

The age and value axes are as in geom_pyramid(), and the side of each line comes from side, fill or colour, as described in position_pyramid(). The line is styled by colour, linewidth, linetype and alpha.

See also

geom_pyramid() for the bars.

Examples

library(ggplot2)

france <- subset(europe_pop, country == "France")

# 2024 as bars, 2004 as an outline
ggplot(france, aes(x = population, y = age, fill = sex)) +
  geom_pyramid(data = subset(france, year == 2024)) +
  geom_pyramid_outline(data = subset(france, year == 2004)) +
  coord_pyramid(age_axis = "centre")