colourScale function

Create colour scales

Produces a scale of colours for plotting maps

colourScale(x, breaks=5, style=c("quantile","equal","unique", "fixed"),
         col="YlOrRd", opacity=1, dec=NULL, digits = 6, firstBreak=NULL, 
         transform=NULL, revCol=FALSE, exclude=NULL, labels=NULL, ...)
        colorScale(...)
        breaksForRates(x, breaks = 10, transform = 0.1,
      multiples = c(2, 4, 5, 10))

Arguments

• x: A vector or single-layer Raster, numeric or factor, for which a colour scale will be created
• breaks: For colourScale either the number of or vector of breaks. for legendBreaks usually the output of colourScale, or a vector of breaks
• style: Style for breaks, see Details
• col: Colours to use, either a function or argument for brewer.pal
• opacity: adds transparency to colours, either a single number, vector of length 2, or vector of same length as breaks
• dec: Number of decimal places for the breaks
• digits: Number of significant figures
• firstBreak: If non-null, force the first break to take this value (often zero).
• transform: A list of two functions to transform x and inverse transform the breaks, or a numeric value specifying a Box-Cox parameter.
• revCol: Reverse the order of the colours.
• exclude: A vector of values to change to NA when they appear in x
• labels: Vector of names of levels, useful when style='unique'
• multiples: break points must be multiples of these numbers times a power of 10
• ...: Additional arguments passed to classIntervals.

Details

colourScale produces intervals from x, each with a unique colour. Categories are determined with break points according to the following style options:

• quantile: quantile(x, prob=seq(0,1,len=breaks), )

equal: seq(min(x), max(x), len=breaks)

unique: sort(table(unique(x)))[1:breaks]

fixed: breaks

any other string: is passed to classIntervals

colorScale passes all it's arguments to colourScale

breaksForRates returns break points suitable for mapping incidence rates, which are positive and always include 1.0.

Returns

A list with elements - plot: Vector of same length of x containing colours (RGB hex)

• breaks: vector of break points

• col: vector of unique colour values corresponding to breaks

• colWithOpacity: as col, but with two digit transparency values appended.

See Also

legendBreaks,scaleBar, classIntervals

Examples

breaksForRates(13.6, breaks = 7) 

Npoints = 20

myPoints = vect(
        cbind(runif(Npoints), 51+runif(Npoints)), 
        atts=data.frame(
                y1=c(NA, rnorm(Npoints-1)), 
            y2=c(sample(0:5, Npoints-1,replace=TRUE), NA)
        ),
        crs=crsLL)


if(require('RColorBrewer', quietly=TRUE)) {
        theCol = 'RdYlBu'
} else {
        theCol = grDevices::heat.colors
}

myscale = colourScale(myPoints$y1, breaks=4, col=theCol,
 style="quantile", revCol=TRUE,dec=1)

data("netherlands")
nldElev = terra::unwrap(nldElev)
myscale = colourScale(nldElev, breaks=4, col=theCol, style='equal', dec=0)

oldpar = map.new(myPoints)
plot(myPoints, col=myscale$plot, pch=16,add=TRUE)
legendBreaks("topleft", myscale)

myscale2 = colourScale(myPoints$y1, breaks=8, col=rainbow, style="equal",
opacity=0.8, dec=2, revCol=TRUE)

map.new(myPoints)
plot(myPoints, col=myscale2$plot, pch=16,add=TRUE)
legendBreaks("topleft", myscale2)

if(require('RColorBrewer', quietly=TRUE)) {
        theCol = 'Set2'
} else {
        theCol = grDevices::heat.colors
}

myscale3 = colourScale(myPoints$y2,  breaks=3,col=theCol, style="unique",
        opacity=c(0.1, 0.9))

map.new(myPoints)
plot(myPoints, col=myscale3$plot, pch=16,add=TRUE)
legendBreaks("topleft", myscale3)

myPoints$y3 = exp(myPoints$y1)
myscale4 = colourScale(myPoints$y3,  breaks=4, style="equal",
        opacity=c(0.1, 0.9), transform=1.25,dec=0, firstBreak=0)

map.new(myPoints)
plot(myPoints, col=myscale4$plot, pch=16,add=TRUE)
legendBreaks("topleft", myscale4)

# raster with colour table

x = rast(extent=ext(0,15,0,10), res=1)
values(x) = sample(1:4, ncell(x), replace=TRUE)
myScale = colourScale(x, breaks=3, style='unique', col=c('red','blue','orange'))
if(utils::packageVersion("terra") >= "1.7-40" ) {
        terra::coltab(x) = myScale$colourtable
        plot(x)
} else {
        plot(x, breaks = myScale$breaks, col=myScale$col)
}
legendBreaks('topright', myScale)

par(oldpar)