maptools: lineLabel – R documentation

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lineLabel

Line label placement with spplot and lattice.

Description

The lineLabel function produces and draws text grobs following the paths defined by a list of Line objects. The sp.lineLabel methods use this function to work easily with spplot.

Usage

lineLabel(line, label,
          spar=.6, position = c('above', 'below'),
          textloc = 'constantSlope',
          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$fontface,
          lty = add.line$lty,
          lwd = add.line$lwd, 
          col.line = add.line$col,
          identifier = 'lineLabel',
          ...)

sp.lineLabel(object, labels, byid=TRUE,...)

label(object, text, ...)

Arguments

`line`	a `list` of `Lines`.
`object`	A `Lines` or `SpatialLines` object.
`label, labels, text`	a string or expression to be printed following the path of `line`. The `names` of `labels` should match the values of the `ID` slot of the lines to label. If `labels` is missing, the `ID` slot is used instead. The `label` method is a wrapper function to extract the `ID` slots and create a suitable `character` object with the correct `names` values.
`byid`	If TRUE (default) only the longest line of each unique `ID` value will be labelled.
`textloc`	a character or a numeric. It may be 'constantSlope', 'minSlope' or 'maxDepth', or the numeric index of the location. If it is a numeric, its length must coincide with the number of `Lines`.
`spar`	smoothing parameter. With values near zero, the label will closely follow the line. Default value is .6. See smooth.spline for details.
`position`	character string ('above' or 'below') to define where the text must be placed.
`col, alpha, cex, lineheight, font, fontfamily, fontface`	graphical arguments for the text. See gpar for details.
`lty, lwd, col.line`	graphical parameters for the line. See gpar for details.
`identifier`	A character string to identify the grob to be created.
`...`	other arguments

Details

Part of the label location code is adapted from panel.levelplot. smooth.spline is used to resample the segment of the line where the label is placed.

Author(s)

Oscar Perpiñán Lamigueiro.

Examples

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

data(meuse)
coordinates(meuse) = ~x+y
data(meuse.riv)
meuse.sl <- SpatialLines(list(Lines(list(Line(meuse.riv)), "1")))

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

labs <- label(meuse.sl, 'Meuse River')

## Maximum depth
sl1 <- list('sp.lineLabel', meuse.sl, label=labs,
            position='below', textloc='maxDepth',
            spar=.2,
            col='darkblue', cex=1,
            fontfamily='Palatino',
            fontface=2)

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

## Constant slope
sl2 <- modifyList(sl1, list(textloc = 'constantSlope')) ## Default

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

## Location defined by its numeric index
sl3 <- modifyList(sl1, list(textloc = 140, position='above'))

spplot(meuse.grid["dist"],
       col.regions=myCols, 
       sp.layout = sl3)

maptools

Tools for Handling Spatial Objects

v1.1-1

GPL (>= 2)

Authors

Roger Bivand [cre, aut] (<https://orcid.org/0000-0003-2392-6140>), Nicholas Lewin-Koh [aut], Edzer Pebesma [ctb], Eric Archer [ctb], Adrian Baddeley [ctb], Nick Bearman [ctb], Hans-Jörg Bibiko [ctb], Steven Brey [ctb], Jonathan Callahan [ctb], German Carrillo [ctb], Stéphane Dray [ctb], David Forrest [ctb], Michael Friendly [ctb], Patrick Giraudoux [ctb], Duncan Golicher [ctb], Virgilio Gómez Rubio [ctb], Patrick Hausmann [ctb], Karl Ove Hufthammer [ctb], Thomas Jagger [ctb], Kent Johnson [ctb], Matthew Lewis [ctb] (<https://orcid.org/0000-0003-2244-4078>), Sebastian Luque [ctb], Don MacQueen [ctb], Andrew Niccolai [ctb], Edzer Pebesma [ctb], Oscar Perpiñán Lamigueiro [ctb], Ethan Plunkett [ctb], Ege Rubak [ctb] (<https://orcid.org/0000-0002-6675-533X>), Tom Short [ctb], Greg Snow [ctb], Ben Stabler [ctb], Murray Stokely [ctb], Rolf Turner [ctb]

Initial release

2021-03-14