Density Contour Lines

Computes and draws density contour lines.

Usage

ternary_density(x, y, z, ...)

# S4 method for class 'numeric,numeric,numeric'
ternary_density(
  x,
  y,
  z,
  h = NULL,
  n = 25,
  nlevels = 10,
  levels = NULL,
  palette = function(i) grDevices::hcl.colors(i, "YlOrRd", rev = TRUE),
  ...
)

# S4 method for class 'ANY,missing,missing'
ternary_density(
  x,
  h = NULL,
  n = 25,
  nlevels = 10,
  levels = NULL,
  palette = function(i) grDevices::hcl.colors(i, "YlOrRd", rev = TRUE),
  ...
)

Source

Two-dimensional kernel density estimation is adapted from MASS::kde2d().

Arguments

x, y, z

A numeric vector giving the x, y and z ternary coordinates of a set of points. If y and z are missing, an attempt is made to interpret x in a suitable way (see grDevices::xyz.coords()).

...

Further arguments to be passed to ternary_lines().

h

A length-one numeric vector giving the bandwidth.

n

A length-one numeric specifying the number of grid points.

nlevels

A length-one numeric vector specifying the number of contour levels desired. Only used if levels is NULL.

levels

A numeric vector of levels at which to draw contour lines.

palette

A color palette function that takes a single integer argument (the number of levels) and returns a vector of colors.

Value

ternary_density() is called it for its side-effects.

Invisibly returns a list with elements levels (the contour levels) and colors (the contour colors) that can be used for a legend.

Details

Two-dimensional kernel density estimation with an axis-aligned bivariate normal kernel. Normal kernel is evaluated on a square grid, after an isometric log ratio transformation of the original data.

Note

This must be considered as experimental and subject to major changes in a future release.

See also

grDevices::contourLines()

Other statistics: ternary_contour(), ternary_ellipse(), ternary_hull(), ternary_mean(), ternary_pca()

Author

N. Frerebeau

Examples

## Add density
## Data from Aitchison 1986
ternary_plot(lava, panel.first = ternary_grid())
levels <- ternary_density(lava, n = 500, nlevels = 10)

## Add a legend
legend_image <- grDevices::as.raster(rev(levels$colors))
graphics::rasterImage(legend_image, 0.85, 0.75, 0.9, 1)
graphics::text(x = 0.9, y = c(0.75, 1), labels = range(levels$levels), pos = 4)