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Polar coordinates

Source: R/coord.R
coord_polar.Rd

coord_polar() projects the panel into polar space: one position aesthetic becomes the angle and the other the radius. With theta = "x" (the default) the x aesthetic maps to angle and y to radius — a categorical bar chart becomes a wind-rose / coxcomb, a line becomes a radar/spider trace, a point cloud is positioned by (angle, radius). With theta = "y" a stacked bar becomes a pie (see also the mark_pie() / mark_donut() shortcuts). The panel is locked to a square. Lines, areas, and ribbons are interpolated into smooth arcs.

coord_radial() is a fuller polar system (ggplot2 3.5's name): besides theta/start/direction it takes end to sweep only a partial arc (e.g. a half-circle gauge) and inner_radius to open a donut hole. With end = NULL and inner_radius = 0 it is identical to coord_polar().

Usage

coord_polar(plot, theta = "x", start = 0, direction = 1)

coord_radial(
  plot,
  theta = "x",
  start = 0,
  end = NULL,
  direction = 1,
  inner_radius = 0
)

Arguments

plot

A PlotSpec.

theta

Which position aesthetic drives the angle: "x" (default) or "y".

start

Angular offset of the zero position, in radians (0 places the first value at twelve o'clock).

direction

Winding direction: 1 for clockwise (default), -1 for counter-clockwise.

end

Arc end angle in radians; NULL (default) sweeps a full turn from start. Set it for a partial arc — e.g. start = -pi/2, end = pi/2 for a semicircular gauge.

inner_radius

Radius of the central hole as a fraction of the outer radius (0–1); 0 (default) is a filled disc, > 0 a donut/ring.

Value

The modified PlotSpec.

See also

mark_pie(), mark_donut()

Examples

vplot(mtcars) |> mark_bar(x = factor(cyl)) |> coord_polar(theta = "x")

vplot(mtcars) |>
  mark_bar(x = factor(cyl)) |>
  coord_radial(theta = "x", inner_radius = 0.3)