Label placement with spplot and lattice.

Description

Use optimization routines to find good locations for point labels without overlaps.

Usage

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panel.pointLabel(x, y = NULL,
                              labels = seq(along = x),
                              method = c("SANN", "GA"),
                              allowSmallOverlap = FALSE,
                              col = add.text$col,
                              alpha = add.text$alpha,
                              cex = add.text$cex,
                              lineheight = add.text$lineheight,
                              font = add.text$font,
                              fontfamily = add.text$fontfamily,
                              fontface = add.text$fontface,
                              fill='transparent',
                              ...)

sp.pointLabel(object, labels, ...)

Arguments

object

A SpatialPoints object.

x, y

coordinates for the point labels. See xy.coords for details.

labels

a character vector or expression.

method

the optimization method, either SANN for simulated annealing (the default) or GA for a genetic algorithm.

allowSmallOverlap

logical; if TRUE, labels are allowed a small overlap. The overlap allowed is 2% of the diagonal distance of the plot area.

col, alpha, cex, lineheight, font, fontfamily, fontface, fill

Graphical arguments. See gpar for details

...

Additional arguments (currently not processed).

Author(s)

Tom Short wrote pointLabel for base graphics. Oscar Perpiñán Lamigueiro modified this function for lattice and spplot.

See Also

spplot pointLabel

Examples

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n <- 15
x <- rnorm(n)*10
y <- rnorm(n)*10
labels <- as.character(round(x, 5))


myTheme <- list(add.text=list(
                  cex=0.7,
                  col='midnightblue',
                  fontface=2,
                  fontfamily='mono'))
library(lattice)
xyplot(y~x,
       labels=labels,
       par.settings=myTheme, 
       panel=function(x, y, labels, ...){
         panel.xyplot(x, y, ...)
         panel.pointLabel(x, y, labels=labels, ...)
       })



data(meuse.grid)
coordinates(meuse.grid) = ~x+y
proj4string(meuse.grid) <- CRS("+init=epsg:28992")
gridded(meuse.grid) = TRUE

library(RColorBrewer)
myCols <- adjustcolor(colorRampPalette(brewer.pal(n=9, 'Reds'))(100), .85)

pts <- spsample(meuse.grid, n=15, type="random")

Rauthors <- readLines(file.path(R.home("doc"), "AUTHORS"))[9:28]
someAuthors <- Rauthors[seq_along(pts)]

sl1 <- list('sp.points', pts, pch=19, cex=.8, col='midnightblue')
sl2 <- list('sp.pointLabel', pts, label=someAuthors,
            cex=0.7, col='midnightblue',
            fontfamily='Palatino')

spplot(meuse.grid["dist"], col.regions=myCols, sp.layout=list(sl1, sl2))

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