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.

Usage

openColours(scheme = "default", n = 100)

Arguments

scheme: Any one of the pre-defined openair schemes (e.g., "increment") or a user-defined palette (e.g., c("red", "orange", "gold")). See ?openColours for a full list of available schemes.
n: number of colours required.

Value

A character vector of hex codes

Schemes

The following schemes are made available by openColours():

Sequential Colours:

"default", "increment", "brewer1", "heat", "jet", "turbo", "hue", "greyscale".
Simplified versions of the viridis colours: "viridis", "plasma", "magma", "inferno", "cividis", and "turbo".
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".

Diverging Palettes:

Simplified versions of the RColorBrewer diverging palettes: "BrBG", "PiYG", "PRGn", "PuOr", "RdBu", "RdGy", "RdYlBu", "RdYlGn", "Spectral".

Qualitative Palettes:

Simplified versions of the RColorBrewer qualitative palettes: "Accent", "Dark2", "Paired", "Pastel1", "Pastel2", "Set1", "Set2", "Set3".
"cbPalette", a colour-blind safe palette based on the work of https://www.nature.com/articles/nmeth.1618

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://uk-air.defra.gov.uk/air-pollution/daqi 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) --- see ?brewer.pal for actual details. 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

https://colorbrewer2.org/

https://uk-air.defra.gov.uk/air-pollution/daqi

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

Author

David Carslaw

Jack Davison

Examples


# to return 5 colours from the "jet" scheme:
cols <- openColours("jet", 5)
cols
#> [1] "#00007F" "#007FFF" "#7FFF7F" "#FF7F00" "#7F0000"

# to interpolate between named colours e.g. 10 colours from yellow to
#  green to red:
cols <- openColours(c("yellow", "green", "red"), 10)
cols
#>  [1] "#FFFF00" "#C6FF00" "#8DFF00" "#55FF00" "#1CFF00" "#1CE200" "#54AA00"
#>  [8] "#8D7100" "#C63800" "#FF0000"