colourScale: Create colour scales

Description

Produces a scale of colours for plotting maps an producing legends.

Usage

colourScale(x, breaks=5, style=c("quantile","equal","unique", "fixed"),
	 col="YlOrRd", opacity=1, dec=NULL, firstBreak=NULL, 
	 transform=NULL, revCol=FALSE, exclude=NULL, labels=NULL,...)
legendBreaks(pos, breaks, outer=TRUE,...)

Arguments

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

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'

pos

Position, as specified in the legend function.

outer

If TRUE, put legend in the margin of the plot

...

Additional arguments passed to classIntervals or legend.

Value

A list with elements
plotVector of same length of x containing colours (RGB hex)
breaksvector of break points
colvector of unique colour values corresponding to breaks
colWithOpacityas col, but with two digit transparency values appended.

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

legendBreaks produces a legend for 'z-axis' colour scales.

Examples

Run this code

Npoints = 20
myPoints = SpatialPointsDataFrame(20*cbind(runif(Npoints), runif(Npoints)), 
	data=data.frame(y1=c(NA, rnorm(Npoints-1)), 
	y2=c(sample(1:4, Npoints-1,replace=TRUE), NA)),
	proj4string=CRS("+proj=longlat +datum=WGS84 +no_defs +ellps=WGS84 +towgs84=0,0,0")
	)

mymap = openmap(myPoints)

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

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



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


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

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

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

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

map.new(myPoints)
plot(mymap,add=TRUE)
plot(myPoints, col=myscale3$plot, pch=16,add=TRUE)
legendBreaks("topleft", breaks=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(mymap,add=TRUE)
plot(myPoints, col=myscale4$plot, pch=16,add=TRUE)
legendBreaks("topleft", breaks=myscale4$breaks, col=myscale4$col)