scale_tol_smoothrainbow {khroma}

Paul Tol's smooth rainbow Sequential Color Scheme

Description

Paul Tol's smooth rainbow Sequential Color Scheme

Usage

scale_colour_smoothrainbow(
  ...,
  reverse = FALSE,
  range = c(0, 1),
  discrete = FALSE,
  aesthetics = "colour"
)

scale_color_smoothrainbow(
  ...,
  reverse = FALSE,
  range = c(0, 1),
  discrete = FALSE,
  aesthetics = "colour"
)

scale_fill_smoothrainbow(
  ...,
  reverse = FALSE,
  range = c(0, 1),
  discrete = FALSE,
  aesthetics = "fill"
)

scale_edge_colour_smoothrainbow(
  ...,
  reverse = FALSE,
  range = c(0, 1),
  discrete = FALSE,
  aesthetics = "edge_colour"
)

scale_edge_color_smoothrainbow(
  ...,
  reverse = FALSE,
  range = c(0, 1),
  discrete = FALSE,
  aesthetics = "edge_colour"
)

scale_edge_fill_smoothrainbow(
  ...,
  reverse = FALSE,
  range = c(0, 1),
  discrete = FALSE,
  aesthetics = "edge_fill"
)

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.

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.

aesthetics

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

Value

A continuous scale.

Sequential Color Schemes

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.

Palette	Max.	NA value
YlOrBr	9	#888888
iridescent	23	#999999
discreterainbow	23	#777777
smoothrainbow	34	#666666

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.

Author(s)

N. Frerebeau

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 sequential color schemes: scale_crameri_acton, scale_crameri_bamako, scale_crameri_batlow, scale_crameri_batlowK, scale_crameri_batlowW, scale_crameri_bilbao, scale_crameri_buda, scale_crameri_davos, scale_crameri_devon, scale_crameri_grayC, scale_crameri_hawaii, scale_crameri_imola, scale_crameri_lajolla, scale_crameri_lapaz, scale_crameri_nuuk, scale_crameri_oslo, scale_crameri_tokyo, scale_crameri_turku, scale_tol_YlOrBr, scale_tol_incandescent, scale_tol_iridescent

Other Paul Tol's color schemes: scale_tol_BuRd, scale_tol_PRGn, scale_tol_YlOrBr, scale_tol_bright, scale_tol_dark, scale_tol_discreterainbow, scale_tol_highcontrast, scale_tol_incandescent, scale_tol_iridescent, scale_tol_light, scale_tol_mediumcontrast, scale_tol_muted, scale_tol_nightfall, scale_tol_pale, scale_tol_sunset, scale_tol_vibrant

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))