Jitter points on an ellipse to avoid over-plotting

This function adds elliptical random noise to perfectly over-plotted points, offering a pleasing way to visualize many points that represent the same position. In contrast to the position_jitter() function which samples from a rectangular field, the position_jitter_ellipse() function samples from an elliptical field. This function takes algorithmic inspiration from https://stackoverflow.com/questions/5529148/algorithm-calculate-pseudo-random-point-inside-an-ellipse and https://stats.stackexchange.com/questions/120527/simulate-a-uniform-distribution-on-a-disc.

Usage

position_jitter_ellipse(width = NULL, height = NULL, seed = NA)

Arguments

width, height

The dimensions of the elliptical field, from which over-plotted points are sampled.

seed

A random seed for reproducibility.

Value

A ggproto object of class PositionJitterEllipse.

See also

Other Functions: position_circlepack(), position_circlepackdodge(), position_jitterdodge_ellipse(), position_sunflower(), position_sunflowerdodge(), sunflower()

Examples

  library(ggplot2)

  dat <- data.frame(x = rep(1, 500), y = rep(1, 500))

  # Jitter on an ellipse.
  ggplot(dat, aes(x, y)) +
    geom_point(position = position_jitter_ellipse(width = 0.5, height = 0.5)) +
    coord_cartesian(xlim = c(0, 2), ylim = c(0, 2))


  # Jitter on a rectangle, for comparison.
  ggplot(dat, aes(x, y)) +
    geom_point(position = position_jitter(width = 0.5, height = 0.5)) +
    coord_cartesian(xlim = c(0, 2), ylim = c(0, 2))