Pre-defined openair colours and definition of user-defined colours

This in primarily an internal openair function to make it easy for users to select particular colour schemes, or define their own range of colours of a user-defined length. openColours() and openColors() are synonyms.

Usage

openColours(
  scheme = "default",
  n = NULL,
  alpha = 1,
  begin = 0,
  end = 1,
  direction = 1,
  saturation = 0.5,
  lightness = 0.5
)

openColors(
  scheme = "default",
  n = NULL,
  alpha = 1,
  begin = 0,
  end = 1,
  direction = 1,
  saturation = 0.5,
  lightness = 0.5
)

Arguments

scheme: Any one of the pre-defined openair schemes (e.g., "increment") or a user-defined palette (e.g., c("red", "orange", "gold")). Use openSchemes() for a full list of available schemes.
n: The whole number of colours required. If not provided, sequential palettes will return 100 colours and qualitative palettes will return the maximum number of colours available for that scheme.
alpha: The alpha transparency level (between 0 and 1) for the colours. 0 is fully transparent, and 1 is fully opaque.
begin, end: For sequential schemes, the fraction (between 0 and 1) of the colour scheme to use. For example, if begin = 0.2 and end = 0.8, only the middle 60% of the colour scheme will be used. This can be useful for avoiding very light or dark colours at the ends of schemes.
direction: The order of the colours. 1 is the default and gives the normal order. -1 will reverse the order of the colours.
saturation: The saturation of the colours, between 0 (completely desaturated, i.e., grey) and 1 (completely saturated). The default is 0.5, which gives the original saturation of the colours. Values less than 0.5 will make the colours more desaturated (greyer), and values greater than 0.5 will make the colours more saturated (vibrant).
lightness: The lightness of the colours, between 0 (completely black) and 1 (completely white). The default is 0.5, which gives the original lightness of the colours. Values less than 0.5 will make the colours darker, and values greater than 0.5 will make the colours brighter.

Value

A character vector of hex codes

Schemes

The following schemes are made available by openColours(). This list is also available as a table by using openSchemes().

Sequential Colours:

"default", "increment", "heat", "jet", "turbo", "hue", "greyscale".
Simplified versions of the viridis colours: "viridis", "plasma", "magma", "inferno", "cividis", "turbo", "rocket" and "mako".
Simplified versions of the RColorBrewer sequential palettes: "Blues", "BuGn", "BuPu", "GnBu", "Greens", "Greys", "Oranges", "OrRd", "PuBu", "PuBuGn", "PuRd", "Purples", "RdPu", "Reds", "YlGn", "YlGnBu", "YlOrBr", "YlOrRd".
Simplified versions of Fabio Crameri's sequential palettes: "acton", "bamO", "bamako", "batlow", "batlowK", "batlowW", "bilbao", "brocO", "buda", "corkO", "davos", "devon", "glasgow", "grayC", "hawaii", "imola", "lajolla", "lapaz", "lipari", "navia", "naviaW", "nuuk", "oslo", "romaO", "tokyo", "turku", "vikO".

Diverging Palettes:

Simplified versions of the RColorBrewer diverging palettes: "BrBG", "PiYG", "PRGn", "PuOr", "RdBu", "RdGy", "RdYlBu", "RdYlGn", "Spectral".
Simplified versions of Fabio Crameri's diverging palettes: "bam", "berlin", "broc", "cork", "lisbon", "managua", "roma", "tofino", "vanimo", "vik"

Qualitative Palettes:

Simplified versions of the RColorBrewer qualitative palettes: "Accent", "Dark2", "Paired", "Pastel1", "Pastel2", "Set1", "Set2", "Set3".
"okabeito" (or "cbPalette"), a colour-blind safe palette based on the work of Masataka Okabe and Kei Ito (https://jfly.uni-koeln.de/color/)
"tol.bright" (or "tol"), "tol.highcontrast", "tol.vibrant", "tol.muted", "tol.mediumcontrast", "tol.pale", "tol.dark", and "tol.light"; colour-blind safe palettes based on the work of Paul Tol.
"tableau" and "observable", aliases for the "Tableau10" (https://www.tableau.com/blog/colors-upgrade-tableau-10-56782) and "Observable10" (https://observablehq.com/blog/crafting-data-colors) colour palettes. These could be useful for consistency between openair plots and with figures made in Tableau or Observable Plot.

UK Government Palettes:

"daqi" and "daqi.bands", the colours associated with the UK daily air quality index; "daqi" (a palette of 10 colours, corresponding to each index value) or "daqi.bands" (4 colours, corresponding to each band - Low, Moderate, High, and Very High). These colours were taken directly from https://check-air-quality.service.gov.uk/ and may be useful in figures like calendarPlot().
"gaf.cat", "gaf.focus" and "gaf.seq", colours recommended by the UK Government Analysis function (https://analysisfunction.civilservice.gov.uk/policy-store/data-visualisation-colours-in-charts/). "gaf.cat" will return the 'categorical' palette (max 6 colours), "gaf.focus" the 'focus' palette (max 2 colours), and "gaf.seq" the 'sequential' palette.

Details

Because of the way many of the schemes have been developed they only exist over certain number of colour gradations (typically 3–10). If less than or more than the required number of colours is supplied then openair will interpolate the colours.

Each of the pre-defined schemes have merits and their use will depend on a particular situation. For showing incrementing concentrations, e.g., high concentrations emphasised, then "default", "heat", "jet", "turbo", and "increment" are very useful. See also the description of RColorBrewer schemes for the option scheme.

To colour-code categorical-type problems, e.g., colours for different pollutants, "hue" and "brewer1" are useful.

When publishing in black and white, "greyscale" is often convenient. With most openair functions, as well as generating a greyscale colour gradient, it also resets strip background and other coloured text and lines to greyscale values.

Failing that, the user can define their own schemes based on R colour names. To see the full list of names, type colors() into R.

References

Color Brewer: https://colorbrewer2.org/

DAQI Colours: https://check-air-quality.service.gov.uk/

UK Government Analysis Function: https://analysisfunction.civilservice.gov.uk/policy-store/data-visualisation-colours-in-charts/

Fabio Crameri's Color Schemes: Crameri, F. 2023. Scientific Colour Maps (version 8.0.1). Zenodo. DOI: doi:10.5281/zenodo.1243862 .

Author

David Carslaw

Jack Davison

Examples


# to return 5 colours from the "jet" scheme:
cols <- openColours("jet", 5)
cols
#> [1] "#00007FFF" "#007FFFFF" "#7FFF7FFF" "#FF7F00FF" "#7F0000FF"

# to interpolate between named colours e.g. 10 colours from yellow to
#  green to red:
cols <- openColours(c("yellow", "green", "red"), 10)
cols
#>  [1] "#FFFF00FF" "#C6FF00FF" "#8DFF00FF" "#55FF00FF" "#1CFF00FF" "#1CE200FF"
#>  [7] "#54AA00FF" "#8D7100FF" "#C63800FF" "#FF0000FF"