sunflower: Distribute points using a sunflower seed algorithm

In vayr: Extensions for 'ggplot2' to Visualize as You Randomize

Distribute points using a sunflower seed algorithm

Description

This function distributes points in an ellipse via a sunflower seed algorithm as a solution for over-plotting. To implement the algorithm, this function adapts the code from https://stackoverflow.com/questions/28567166/uniformly-distribute-x-points-inside-a-circle.

Usage

sunflower(x = NULL, y = NULL, density, aspect_ratio)

Arguments

x, y	The identical coordinates of multiple over-plotted points, as vectors, which will be arranged using a sunflower seed algorithm. A vector of length one is returned unchanged, since a point with nothing over-plotting it belongs at its own coordinates.
density	The pattern density.
aspect_ratio	An aspect ratio adjustment to compensate for distortion of the circular arrangement, which might occur when plotting if coord_equal() is not used. A wide aspect ratio (e.g., 2) would adjust for vertical stretching, whereas a tall aspect ratio (e.g., 0.5) would adjust for horizontal stretching. An aspect ratio of 1 is appropriate when no adjustment is required.

Details

This is the engine position_sunflower() runs on, exported so that the arrangement can be computed as data rather than at draw time. Reach for it when another layer needs the arranged coordinates, or when writing a Position class of your own: call it once for x and once for y, as PositionSunflower does. The two calls agree because the arrangement is determined by the number of over-plotted points, so the same point is placed at the same angle in both. The package's other algorithms do not decompose that way and have no equivalent function.

Value

A numeric vector of adjusted x or y positions, computed using a sunflower seed algorithm.

See Also

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

Examples

  library(ggplot2)
  library(dplyr)

  # Arrange the points as data, keeping the position each one came from, so
  # that a second layer can draw from the cell centre out to each point. A
  # position adjustment cannot do this, because it arranges at draw time and
  # the arranged coordinates never reach the data.
  N <- 300

  dat <- data.frame(
    x = sample(1:2, size = N, replace = TRUE),
    y = sample(1:7, size = N, replace = TRUE)
  ) |>
    group_by(x, y) |>
    mutate(
      x_flower = sunflower(x = x, density = 1, aspect_ratio = 1),
      y_flower = sunflower(y = y, density = 1, aspect_ratio = 1)
    )

  ggplot(dat, aes(x_flower, y_flower)) +
    geom_segment(aes(xend = x, yend = y), colour = "grey80") +
    geom_point() +
    coord_equal()

  # To dodge groups as well, use position_sunflowerdodge(), which handles the
  # dodging and the arrangement together and accepts an orientation.

vayr documentation built on Aug. 22, 2026, 1:08 a.m.