2-D density contours

mark_contour() draws iso-density contour lines of a 2-D point cloud (x, y); mark_contour_filled() fills the bands between them. By default the field is a kernel density estimate (needs the MASS package); map a z aesthetic to instead contour a supplied surface over a regular x/y grid. Contours are coloured by level automatically — mark_contour() maps color = after_stat(level), mark_contour_filled() maps fill. Requires the isoband package.

Usage

mark_contour(
  plot,
  ...,
  bins = 10,
  binwidth = NULL,
  breaks = NULL,
  n = 100,
  blend = NULL,
  data = NULL
)

mark_contour_filled(
  plot,
  ...,
  bins = 10,
  binwidth = NULL,
  breaks = NULL,
  n = 100,
  blend = NULL,
  data = NULL
)

Arguments

plot

A PlotSpec (from vplot()).

...

Encodings (tidy-eval): x, y (+ optional z surface, color / fill, linewidth).

bins

Target number of contour levels (when neither breaks nor binwidth is given).

binwidth

Spacing between contour levels, or NULL.

breaks

Explicit contour levels, or NULL to derive from bins / binwidth.

n

Density-estimate grid resolution per axis (KDE mode only).

blend

Optional blend mode for compositing this layer against what is already drawn beneath it (the panel and earlier layers), one of the CSS mix-blend-mode names, e.g. "multiply", "screen", "darken". The whole layer composites as one isolated group (not per element).

data

Optional layer data frame; overrides the plot data for this layer.

Value

The modified PlotSpec.

Examples

vplot(faithful) |>
  mark_point(x = eruptions, y = waiting) |>
  mark_contour(x = eruptions, y = waiting)

vplot(faithful) |> mark_contour_filled(x = eruptions, y = waiting)