marine.colours: Perceptually uniform palettes

In albatross: PARAFAC Analysis of Fluorescence Excitation-Emission Matrices

Perceptually uniform palettes

Description

Create perceptually continuous palettes of R colours.

Usage

  marine.colours(
    n, chroma = 0.65, luminance = c(0.35, 1),
    alpha = 1, gamma = 1, fixup = TRUE
  )
  diverging.colours(
    n, chroma = c(.1, .75), luminance = c(1, .35),
    alpha = 1, gamma = 1, fixup = TRUE
  )

Arguments

n	Number of colours to return.
chroma	Specifies the chroma (how saturated should the colours be) for the palette, a real number between 0 and 1. May also be a two-element vector, in which case the chroma is changed smoothly from start to finish of the resulting palette.
luminance	Specifies the luminance (how bright should the colours be) of the colours constituting the palette. Typically, a two-element vector of real numbers between 0 and 1 to indicate smooth change along the palette, but can also be a fixed number.
alpha	Specifies the transparency of the colours of the palette. As above, can be a fixed number or a two-element vector in the range [0,1]. Typically, fully opaque (alpha=1) colours are used.
gamma	Provides the power coefficient for the hue/chroma/luminance/alpha growth formulae. May be useful when it is needed to sacrifice the perceptual linearity of the palette to provide more contrast for smaller or bigger values on the plot. The gamma-corrected values are obtained by computing 3{x ^ \gamma

x ^ \gammax^γ, 3{x \in [0;1]

Details

The marine.colours palette is used by default by all plot methods (e.g. plot.feem) for FEEM-like data to show absolute values. It is designed to retain perceptual uniformity even after complete desaturation.

The diverging.colours palette is used by plot.feem.resid to display residual values. People with severe colour vision deficiency (tritanopia or monochromacy) won't be able to discern positive and negative branches of the palette, but it's supposed to be legible for people with deuteranopia and protanopia.

Value

A character vector of length n containing colour specifications for use with R graphics functions.

\makefigure

png('man/figures/marinecolours.png', 400, 32) par(mar = rep(0, 4)) n <- 256 image(matrix(seq(n), n), col = albatross::marine.colours(n)) dev.off()

The marine.colours palette at the default values of 3{C_{uv}^* = 0.65chroma = 0.65C_uv^* = 0.65, 3{L^* \in [0.35; 1]

References

Insired by cmocean palette called “haline” (https://matplotlib.org/cmocean/#haline), but using R's implementation of polar CIE-LUV colour space instead of CAM02-UCS.

CUBEHELIX (https://people.phy.cam.ac.uk/dag9/CUBEHELIX/) is a similar technique using BT.601 luminance coefficients and RGB colour space.

See Also

plot.feem, hcl

Examples

  image(volcano, col = marine.colours(256))

albatross documentation built on May 29, 2024, 9:10 a.m.