colourScale: Create colour scales

Description

Produces a scale of colours for plotting maps

Usage

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))

Value

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.

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.

Examples

Run this code


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)