Skip to contents

Provides sequential color scales from Paul Tol's Colour Schemes.

Arguments

...

Arguments passed to ggplot2::continuous_scale().

reverse

A logical scalar. Should the resulting vector of colors be reversed?

range

A length-two numeric vector specifying the fraction of the scheme's color domain to keep.

aesthetics

A character string or vector of character strings listing the name(s) of the aesthetic(s) that this scale works with.

discrete

A logical scalar: should the color scheme be used as a discrete scale? If TRUE, it is a departure from Paul Tol's recommendations and likely a very poor use of color.

Value

A continuous scale.

Details

#'

PaletteMax. colorsNA value
YlOrBr9#888888
iridescent23#999999
discreterainbow23#777777
smoothrainbow34#666666

Interpolation

If more colors than defined are needed from a given scheme, the color coordinates are linearly interpolated to provide a continuous version of the scheme, with the exception of the discrete rainbow scheme (see below).

Note that the default color for NA can be overridden by passing a value to ggplot2::continuous_scale().

Rainbow Color Scheme

As a general rule, ordered data should not be represented using a rainbow scheme. There are three main arguments against such use (Tol 2018):

  • The spectral order of visible light carries no inherent magnitude message.

  • Some bands of almost constant hue with sharp transitions between them, can be perceived as jumps in the data.

  • Color-blind people have difficulty distinguishing some colors of the rainbow.

If such use cannot be avoided, Paul Tol's technical note provides two color schemes that are reasonably clear in color-blind vision. To remain color-blind safe, these two schemes must comply with the following conditions:

discreterainbow

This scheme must not be interpolated.

smoothrainbow

This scheme does not have to be used over the full range.

References

Tol, P. (2018). Colour Schemes. SRON. Technical Note No. SRON/EPS/TN/09-002, issue 3.1. URL: https://personal.sron.nl/~pault/data/colourschemes.pdf

Author

N. Frerebeau

Examples

data(faithfuld, package = "ggplot2")

ggplot2::ggplot(faithfuld, ggplot2::aes(waiting, eruptions, fill = density)) +
  ggplot2::geom_raster() +
  scale_fill_YlOrBr()


ggplot2::ggplot(faithfuld, ggplot2::aes(waiting, eruptions, fill = density)) +
  ggplot2::geom_raster() +
  scale_fill_iridescent(reverse = TRUE)


ggplot2::ggplot(faithfuld, ggplot2::aes(waiting, eruptions, fill = density)) +
  ggplot2::geom_raster() +
  scale_fill_smoothrainbow(range = c(0.25, 1))