Paul Tol's Sequential Color Schemes for ggplot2 and ggraph
Source:R/scale_colour_tol.R
scale_tol_sequential.Rd
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? IfTRUE
, it is a departure from Paul Tol's recommendations and likely a very poor use of color.
Value
A continuous scale.
Details
#'
Palette | Max. colors | NA value |
YlOrBr | 9 | #888888 |
iridescent | 23 | #999999 |
discreterainbow | 23 | #777777 |
smoothrainbow | 34 | #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
See also
Other color-blind safe color schemes:
scale_crameri_cyclic
,
scale_crameri_diverging
,
scale_crameri_mutlisequential
,
scale_crameri_sequential
,
scale_okabeito_discrete
,
scale_tol_discrete
,
scale_tol_diverging
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))