grDevices (version 3.3.1)

Palettes: Color Palettes

Description

Create a vector of n contiguous colors.

Usage

rainbow(n, s = 1, v = 1, start = 0, end = max(1, n - 1)/n, alpha = 1)
heat.colors(n, alpha = 1)
terrain.colors(n, alpha = 1)
topo.colors(n, alpha = 1)
cm.colors(n, alpha = 1)

Arguments

n

the number of colors ($\ge 1$) to be in the palette.

s, v

the ‘saturation’ and ‘value’ to be used to complete the HSV color descriptions.

start

the (corrected) hue in [0,1] at which the rainbow begins.

end

the (corrected) hue in [0,1] at which the rainbow ends.

alpha

the alpha transparency, a number in [0,1], see argument alpha in hsv.

Value

cv, of color names. This can be used either to create a user--defined color palette for subsequent graphics by palette(cv), a col = specification in graphics functions or in par.

Details

Conceptually, all of these functions actually use (parts of) a line cut out of the 3-dimensional color space, parametrized by hsv(h, s, v), and hence equispaced hues in RGB space tend to cluster at the red, green and blue primaries.

Some applications such as contouring require a palette of colors which do not wrap around to give a final color close to the starting one.

With rainbow, the parameters start and end can be used to specify particular subranges of hues. The following values can be used when generating such a subrange: red = 0, yellow = $1/6$, green = $2/6$, cyan = $3/6$, blue = $4/6$ and magenta = $5/6$.

See Also

colors, palette, hsv, hcl, rgb, gray and col2rgb for translating to RGB numbers.

Examples

require(graphics)
# A Color Wheel
pie(rep(1, 12), col = rainbow(12))

##------ Some palettes ------------
demo.pal <-
  function(n, border = if (n < 32) "light gray" else NA,
           main = paste("color palettes;  n=", n),
           ch.col = c("rainbow(n, start=.7, end=.1)", "heat.colors(n)",
                      "terrain.colors(n)", "topo.colors(n)",
                      "cm.colors(n)"))
{
    nt <- length(ch.col)
    i <- 1:n; j <- n / nt; d <- j/6; dy <- 2*d
    plot(i, i+d, type = "n", yaxt = "n", ylab = "", main = main)
    for (k in 1:nt) {
        rect(i-.5, (k-1)*j+ dy, i+.4, k*j,
             col = eval(parse(text = ch.col[k])), border = border)
        text(2*j,  k * j + dy/4, ch.col[k])
    }
}
n <- if(.Device == "postscript") 64 else 16
     # Since for screen, larger n may give color allocation problem
demo.pal(n)