rainbow_hcl

From colorspace v0.9 by Ross Ihaka

HCL and HSV Color Palettes

Color palettes based on the HCL and HSV color spaces.

Keywords: color

Usage

rainbow_hcl(n, c = 50, l = 70, start = 0, end = 360*(n-1)/n,
  gamma = 2.4, fixup = TRUE, ...)
sequential_hcl(n, h = 260, c. = c(80, 0), l = c(30, 90), power = 1.5,
  gamma = 2.4, fixup = TRUE, ...)
heat_hcl(n, h = c(0, 90), c. = c(100, 30), l = c(50, 90), power = c(1/5, 1),
  gamma = 2.4, fixup = TRUE, ...)
terrain_hcl(n, h = c(130, 0), c. = c(80, 0), l = c(60, 95), power = c(1/10, 1),
  gamma = 2.4, fixup = TRUE, ...)
diverge_hcl(n, h = c(260, 0), c = 80, l = c(30, 90), power = 1.5,
  gamma = 2.4, fixup = TRUE, ...)
diverge_hsv(n, h = c(240, 0), s = 1, v = 1, power = 1,
  gamma = 2.4, fixup = TRUE, ...)

Arguments

n: the number of colors ($\ge 1$) to be in the palette.
c, c.: chroma value in the HCL color description.
l: luminance value in the HCL color description.
start: the hue at which the rainbow begins.
end: the hue at which the rainbow ends.
h: hue value in the HCL or HSV color description, has to be in [0, 360] for HCL and in [0, 1] for HSV colors.
s: saturation value in the HSV color description.
v: value value in the HSV color description.
power: control parameter determining how chroma and luminance should be increased (1 = linear, 2 = quadratic, etc.).
gamma: gamma value of the display.
fixup: logical. Should the color be corrected to a valid RGB value before correction?
...: Other arguments passed to hex.

Details

All functions compute palettes based on either the HCL (polarLUV) or the HSV (HSV) color space. rainbow_hcl computes a rainbow of colors (qualitative palette) defined by different hues given a single value of each chroma and luminance. It corresponds to rainbow which computes a rainbow in HSV space.

sequential_hcl gives a sequential palette starting at the full color HCL(h, c[1], l[1]) through to a light color HCL(h, c[2], l[2]) by interpolation. diverge_hcl and diverge_hsv, compute a set of colors diverging from a neutral center (grey or white, without color) to two different extreme colors (blue and red by default). This is similar to cm.colors. For the diverging HSV colors, two hues h are needed, a maximal saturation s and a fixed value v. The saturation is then varied to obtain the diverging colors. For the diverging HCL colors, again two hues h are needed, a maximal chroma c and two luminances l. The colors are then created by an interpolation between the full color HCL(h[1], c, l[1]), a neutral color HCL(h, 0, l[2]) and the other full color HCL(h[2], c, l[1]).

The palette heat_hcl gives an implementation of heat.colors in HCL space. By default, it goes from a red to a yellow hue, while simultaneously going to lighter colors (i.e., increasing luminance) and reducing the amount of color (i.e., decreasing chroma). The terrain_hcl palette simply calls heat_hcl with different parameters, providing colors similar in spirit to terrain.colors. The lighter colors are not strictly HCL colors, though.

Value

A character vector with (s)RGB codings of the colors in the palette.

encoding

UTF-8

References

Zeileis A., Hornik K. and Murrell P. (2007), Escaping RGBland: Selecting Colors for Statistical Graphics. Report 61, Department of Statistics and Mathematics, Wirtschaftsuniversität Wien, Research Report Series, http://epub.wu-wien.ac.at/.

Examples

## convenience demo functions
wheel <- function(col, radius = 1, ...)
  pie(rep(1, length(col)), col = col, radius = radius, ...) 

pal <- function(col, border = "light gray")
{
  n <- length(col)
  plot(0, 0, type="n", xlim = c(0, 1), ylim = c(0, 1), axes = FALSE, xlab = "", ylab = "")
  rect(0:(n-1)/n, 0, 1:n/n, 1, col = col, border = border)
}

## qualitative palette
wheel(rainbow_hcl(12))

## a few useful diverging HCL palettes
par(mar = rep(0, 4), mfrow = c(4, 1))
pal(diverge_hcl(7))
pal(diverge_hcl(7, h = c(246, 40), c = 96, l = c(65, 90)))
pal(diverge_hcl(7, h = c(130, 43), c = 100, l = c(70, 90)))
pal(diverge_hcl(7, h = c(180, 70), c = 70, l = c(90, 95)))
pal(diverge_hcl(7, h = c(180, 330), c = 59, l = c(75, 95)))
pal(diverge_hcl(7, h = c(128, 330), c = 98, l = c(65, 90)))
pal(diverge_hcl(7, h = c(255, 330), l = c(40, 90)))
pal(diverge_hcl(7, c = 100, l = c(50, 90), power = 1))

## sequential palettes
pal(sequential_hcl(12))
pal(heat_hcl(12, h = c(0, -100), l = c(75, 40), c = c(40, 80), power = 1))
pal(terrain_hcl(12, c = c(65, 0), l = c(45, 95), power = c(1/3, 1.5)))
pal(heat_hcl(12, c = c(80, 30), l = c(30, 90), power = c(1/5, 1.5)))

## compare base and vcd palettes
par(mfrow = c(2, 1))
wheel(rainbow(12)); wheel(rainbow_hcl(12))
pal(diverge_hcl(7, c = 100, l = c(50, 90))); pal(diverge_hsv(7))
pal(diverge_hcl(7, h = c(180, 330), c = 59, l = c(75, 95))); pal(cm.colors(7))
pal(heat_hcl(12)); pal(heat.colors(12))
pal(terrain_hcl(12)); pal(terrain.colors(12))

Documentation reproduced from package colorspace, version 0.9, License: BSD

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