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(scheme = "default", n = 100)A character vector of hex codes
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.
number of colours required.
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.
David Carslaw
Jack Davison
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.
https://uk-air.defra.gov.uk/air-pollution/daqi
https://analysisfunction.civilservice.gov.uk/policy-store/data-visualisation-colours-in-charts/
# to return 5 colours from the "jet" scheme:
cols <- openColours("jet", 5)
cols
# to interpolate between named colours e.g. 10 colours from yellow to
# green to red:
cols <- openColours(c("yellow", "green", "red"), 10)
cols
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