Color Palette

Provides qualitative, diverging and sequential color schemes.

Usage

colour(palette, reverse = FALSE, names = TRUE, lang = "en", force = FALSE, ...)

color(palette, reverse = FALSE, names = TRUE, lang = "en", force = FALSE, ...)

Arguments

palette: A character string giving the name of the palette to be used (see below).
reverse: A logical scalar: should the resulting vector of colors should be reversed?
names: A logical scalar: should the names of the colors should be kept in the resulting vector?
lang: A character string specifying the language for the color names. It must be one of "en" (English, the default) or "fr" (French).
force: A logical scalar. If TRUE, forces the color scheme to be interpolated. It should not be used routinely with qualitative color schemes, as they are designed to be used as is to remain color-blind safe.
...: Further arguments passed to colorRampPalette.

Value

A palette function with the following attributes, that when called with a single integer argument (the number of levels) returns a (named) vector of colors.

palette: A character string giving the name of the color scheme.
type: A character string giving the corresponding data type. One of "qualitative", "diverging" or "sequential".
interpolate: A logical scalar: can the color palette be interpolated?
missing: A character string giving the the hexadecimal representation of the color that should be used for NA values.
max: An integer giving the maximum number of color values. Only relevant for non-interpolated color schemes.

For color schemes that can be interpolated (diverging and sequential data), the color range can be limited with an additional argument. range allows to remove a fraction of the color domain (before being interpolated; see examples).

Paul Tol's Color Schemes

The following palettes are available. The maximum number of supported colors is in brackets, this value is only relevant for the qualitative color schemes (divergent and sequential schemes are linearly interpolated).

Qualitative data: bright (7), high contrast (3), vibrant (7), muted (9), medium contrast (6), pale (6), dark (6), light (9).
Diverging data: sunset (11), nightfall (17), BuRd (9), PRGn (9).
Sequential data: YlOrBr (9), iridescent (23), incandescent (11), discrete rainbow (23), smooth rainbow (34).

Qualitative Color Schemes

According to Paul Tol's technical note, the bright, highcontrast, vibrant and muted color schemes are color-blind safe. The mediumcontrast color scheme is designed for situations needing color pairs.

The light color scheme is reasonably distinct for both normal or colorblind vision and is intended to fill labeled cells.

The pale and dark schemes are not very distinct in either normal or colorblind vision and should be used as a text background or to highlight a cell in a table.

Refer to the original document for details about the recommended uses (see references).

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.

Okabe and Ito Color Scheme

The following (qualitative) color scheme is available:

okabeito: Up to 8 colors.
okabeito black: Up to 8 colors, with black as the last.

Scientific Color Schemes

The following (qualitative) color schemes are available:

stratigraphy: International Chronostratigraphic Chart (175 colors).
land: AVHRR Global Land Cover Classification (14 colors).
soil: FAO Reference Soil Groups (24 colors).

References

Jones, A., Montanarella, L. & Jones, R. (Ed.) (2005). Soil atlas of Europe. Luxembourg: European Commission, Office for Official Publications of the European Communities. 128 pp. ISBN: 92-894-8120-X.

Okabe, M. & Ito, K. (2008). Color Universal Design (CUD): How to Make Figures and Presentations That Are Friendly to Colorblind People. URL: https://jfly.uni-koeln.de/color/.

Tol, P. (2021). Colour Schemes. SRON. Technical Note No. SRON/EPS/TN/09-002, issue 3.2. URL: https://personal.sron.nl/~pault/data/colourschemes.pdf

Commission for the Geological Map of the World

Author

N. Frerebeau

Examples

## Okabe and Ito colour scheme
colour("okabe ito")(8)
#>          black         orange       sky blue   bluish green         yellow 
#>      "#000000"      "#E69F00"      "#56B4E9"      "#009E73"      "#F0E442" 
#>           blue      vermilion reddish purple 
#>      "#0072B2"      "#D55E00"      "#CC79A7" 
#> attr(,"missing")
#> [1] NA
plot_scheme(colour("okabe ito")(8))


## Paul Tol's colour schemes
### Qualitative data
plot_scheme(colour("bright")(7))

plot_scheme(colour("high contrast")(3))

plot_scheme(colour("vibrant")(7))

plot_scheme(colour("muted")(9))

plot_scheme(colour("medium contrast")(6))

plot_scheme(colour("pale")(6))

plot_scheme(colour("dark")(6))

plot_scheme(colour("light")(9))

### Diverging data
plot_scheme(colour("sunset")(11))

plot_scheme(colour("BuRd")(9))

plot_scheme(colour("PRGn")(9))

### Sequential data
plot_scheme(colour("YlOrBr")(9))

plot_scheme(colour("iridescent")(23))

plot_scheme(colour("discrete rainbow")(14))

plot_scheme(colour("discrete rainbow")(23))

plot_scheme(colour("smooth rainbow")(34))


## Scientific colour schemes
### Geologic timescale
plot_scheme(colour("stratigraphy")(175))

### AVHRR global land cover classification
plot_scheme(colour("land")(14))

### FAO soil reference groups
plot_scheme(colour("soil")(24))


## Adjust colour levels
PRGn <- colour("PRGn")
plot_scheme(PRGn(9, range = c(0.5, 1)))