Scatter over-plotted points evenly at random

This function spreads perfectly over-plotted points across an elliptical field, like position_jitter_ellipse(), but places them so that no two land much closer together than the rest. Sampling uniformly at random, which is what jittering does, leaves visible knots and voids: in a draw of 200 points the closest pair typically sits about a fifteenth of the median spacing apart. A reader cannot tell those knots from real structure. The arrangement here has the even spacing of position_sunflower() while still looking unstructured, so no reader mistakes a spiral arm for a finding.

Usage

position_bluenoise(width = NULL, height = NULL, candidates = 10, seed = NA)

Arguments

width, height

The dimensions of the elliptical field the points are spread across.

candidates

The number of random draws considered for each point. Larger values space the points more evenly and take longer. The default of 10 is enough to remove essentially all of the clumping.

seed

A random seed for reproducibility.

Value

A ggproto object of class PositionBlueNoise.

Details

The pattern is the one the eye's own photoreceptors are laid out in, known as blue noise or a Poisson-disc distribution. It is produced by Mitchell's best-candidate algorithm: each point is the best of candidates random draws, where best means farthest from every point already placed.

See also

Other Functions: impute_extreme_values(), position_bluenoisedodge(), position_circlepack(), position_circlepackdodge(), position_honeycomb(), position_honeycombdodge(), position_jitter_ellipse(), position_jitterdodge_ellipse(), position_sunflower(), position_sunflowerdodge(), sunflower()

Examples

  library(ggplot2)

  dat <- data.frame(x = rep(1, 400), y = rep(1, 400))

  # Evenly scattered.
  ggplot(dat, aes(x, y)) +
    geom_point(position = position_bluenoise(width = 0.5, height = 0.5)) +
    coord_equal(xlim = c(0, 2), ylim = c(0, 2))


  # Uniformly jittered, for comparison. Note the knots and the gaps.
  ggplot(dat, aes(x, y)) +
    geom_point(position = position_jitter_ellipse(width = 0.5, height = 0.5)) +
    coord_equal(xlim = c(0, 2), ylim = c(0, 2))