library(khroma)
Tol (2018) offers carefully chosen schemes, ready for each type of data, with colours that are:
All the scales presented in Paul Tol’s technical note (issue 3.1, 2018-09-23) are implemented here, for use with base R graphics or ggplot2.
According to Paul Tol’s technical note, the bright, contrast, vibrant and muted colour schemes are colour-blind safe.
The light colour scheme is reasonably distinct for both normal or colour-blind vision and is intended to fill labelled cells.
The pale and dark schemes are not very distinct in either normal or colour-blind vision and should be used as a text background or to highlight a cell in a table.
The qualitative colour schemes must be used as given (no interpolation): colours are picked up to the maximum number of supported values. Refer to the original document for details about the recommended uses (see references).
Scheme | Max. colours |
---|---|
bright | 7 |
contrast | 3 |
vibrant | 7 |
muted | 9 |
pale | 6 |
dark | 6 |
light | 9 |
<- colour("bright")
bright plot_scheme(bright(7), colours = TRUE, names = TRUE, size = 0.9)
<- colour("contrast")
contrast plot_scheme(contrast(3), colours = TRUE, names = TRUE, size = 0.9)
<- colour("vibrant")
vibrant plot_scheme(vibrant(7), colours = TRUE, names = TRUE, size = 0.9)
<- colour("muted")
muted plot_scheme(muted(9), colours = TRUE, names = TRUE, size = 0.9)
<- colour("light")
light plot_scheme(light(9), colours = TRUE, names = TRUE, size = 0.9)
<- colour("pale")
pale plot_scheme(pale(6), colours = TRUE, names = TRUE, size = 0.9)
<- colour("dark")
dark plot_scheme(dark(6), colours = TRUE, names = TRUE, size = 0.9)
If more colours than defined are needed from a given scheme, the colour coordinates are linearly interpolated to provide a continuous version of the scheme.
Scheme | Num. of colours | Bad data |
---|---|---|
sunset | 11 | #FFFFFF |
BuRd | 9 | #FFEE99 |
PRGn | 9 | #FFEE99 |
<- colour("sunset")
sunset plot_scheme(sunset(9), colours = TRUE, size = 0.9)
<- colour("BuRd")
BuRd plot_scheme(BuRd(9), colours = TRUE, size = 0.9)
<- colour("PRGn")
PRGn plot_scheme(PRGn(9), colours = TRUE, size = 0.9)
If more colours than defined are needed from a given scheme, the colour coordinates are linearly interpolated to provide a continuous version of the scheme, with the exception of the discrete rainbow scheme (see below).
Scheme | Num. of colours | Bad data |
---|---|---|
YlOrBr | 9 | #888888 |
iridescent | 23 | #999999 |
discrete rainbow | 23 | #777777 |
smooth rainbow | 34 | #666666 |
<- colour("YlOrBr")
YlOrBr plot_scheme(YlOrBr(9), colours = TRUE, size = 0.9)
<- colour("iridescent")
iridescent plot_scheme(iridescent(23), colours = TRUE, size = 0.5)
As a general rule, ordered data should not be represented using a rainbow scheme. There are three main arguments against such use (Tol 2018):
If such use cannot be avoided, Paul Tol’s technical note provides two colour schemes that are reasonably clear in colour-blind vision. To remain colour-blind safe, these two schemes must comply with the following conditions:
<- colour("discrete rainbow")
discrete_rainbow plot_scheme(discrete_rainbow(14), colours = TRUE, size = 0.7)
When using the smooth rainbow scheme:
<- colour("smooth rainbow")
smooth_rainbow
# Start at purple instead of off-white
plot(smooth_rainbow(256, range = c(0.25, 1)))
# End at red instead of brown
plot(smooth_rainbow(256, range = c(0, 0.9)))
Diagnostic maps for the bright, vibrant, muted and light (from top to bottom) qualitative colour schemes.
Diagnostic maps for the sunset, BuRd and PRGn (from top to bottom) diverging colour schemes.
Diagnostic maps for the YlOrBr, iridescent, discrete rainbow and smooth rainbow (from top to bottom) sequential colour schemes.