scaleBar function

Scale bar and inset map

Utilities for plotting a map, adding a scale bar and north arrow, and adding a legend of colour scales.

scaleBar(crs, pos = "bottomright",   
        cex=1,
    pt.cex = 1.1*cex,
    seg.len=5*cex,
    title.cex=cex,
    outer=TRUE,...)
insetMap(crs, pos="bottomright",map="osm",zoom=0, 
                width=max(c(0.2, 1-par('plt')[2])), 
                col="#FF000090", borderMap=NULL,
                        cropInset = terra::ext(-180, 180,  -47, 71),
                        outer=TRUE, inset = c(0.1, 0.1), ...)

Arguments

• crs: A character string from which a projection can be extracted with terra::crs

• pos: Position, as specified in the legend function.

• cex: scaling factor for the legend

• pt.cex: Scaling factor north arrow (can be zero).

• seg.len: approximate length (in character units) of the scale bar. can be zero.

• title.cex: scaling for the distance text

• outer: If TRUE, put bar or map in the margin of the plot

• map: Either a Raster for the inset map or a string passed to openmap's path argument

• zoom: Zoom level if retrieving inset map from openmap

• width: Width of the inset map, as a fraction of the plot window

• col: Colour for shaded region of inset map

• borderMap: border style for the inset map (passed to polygon)

• cropInset: Crop the insert map to this extent

• inset: how far from the border to put the inset map

• ...: Additional arguments passed to legend for scaleBar

  or polygon (for insetMap).

Details

scaleBar produces a scale bar reflecting the distance travelling on a great circle from the centre of the plot and travelling to the right. The length of the bar is the width of 6 characters times scale.cex.

Returns

A list containig coordinates of the elements of the scale bar.

Author(s)

Patrick Brown

Examples

Npoints = 20
set.seed(0)
myPoints = vect(
        cbind(runif(Npoints)-0.1, 51+runif(Npoints)), 
        atts=data.frame(
                y1=c(NA, rnorm(Npoints-1)), 
            y2=c(sample(0:5, Npoints-1,replace=TRUE), NA)
        ),
        crs=crsLL)


breaks = c(-100, -1, 1, Inf)
thecol = c('red','orange','blue')

oldpar = map.new(myPoints)
plot(myPoints,col = as.character(cut(
        myPoints$y1, breaks, thecol
)),add=TRUE)
scaleBar(myPoints, "bottomright",cex=1.25, seg.len=2)
legendBreaks("topleft", legend=breaks, col=thecol)

thedot = insetMap(crs=myPoints, 
        pos="bottomleft",
         col='#00000000', lty=0, outer=FALSE, width=0.25)
points(thedot)

par(oldpar)