tmaptools (version 2.0-1)

offset_line: Create a double line or offset line

Description

Create a double line or offset line. The double line can be useful for visualizing two-way tracks or emulating objects such as railway tracks. The offset line can be useful to prevent overlapping of spatial lines. Note that this function supports sf objects, but still uses sp-based methods (see details).

Usage

offset_line(shp, offset)
double_line(shp, width, sides = "both")

Arguments

shp

SpatialLines(DataFrame)

offset

offset from the original lines

width

width between the left and righthand side

sides

character value that specifies which sides are selected: "both", "left", or "right". The default is "both". For the other two options, see also the shortcut function offset_line.

Value

A shape object, in the same format as shp

Details

This function supports sf objects, but still uses sp-based methods, from the packages sp, rgeos, and/or rgdal.

Examples

# NOT RUN {
if (require(tmap)) {
### Demo to visualise the route of the Amstel Gold Race, a professional cycling race
	tmpdir <- tempdir()
	tmpfile <- tempfile()
	download.file("http://www.gpstracks.nl/routes-fiets/f-limburg-amstel-gold-race-2014.zip",
				  tmpfile, mode="wb")
	unzip(tmpfile, exdir=tmpdir)

	# read GPX file
	AGR <- read_GPX(file.path(tmpdir, "f-limburg-amstel-gold-race-2014.gpx"))

	# read OSM of Zuid-Limburg
	Limburg_OSM <- read_osm(AGR$tracks, ext=1.05)

	# change route part names
	levels(AGR$tracks$name) <- paste(c("First", "Second", "Third", "Final"), "loop")
	AGR$tracks_offset2 <- offset_line(AGR$tracks, offset=c(.0005,0,-.0005,-.001))

	tm_shape(Limburg_OSM) +
		tm_raster(saturation=.25) +
	tm_shape(AGR$tracks_offset2) +
		tm_lines(col = "name", lwd = 4, title.col="Amstel Gold Race", palette="Dark2") +
	tm_shape(AGR$waypoints) +
		tm_bubbles(size=.1, col="gold", border.col = "black") +
		tm_text("name", size = .75, bg.color="white", bg.alpha=.25, auto.placement = .25) +
	tm_legend(position=c("right", "top"), frame=TRUE, bg.color = "gold") +
	tm_view(basemaps = "Esri.WorldTopoMap")

	# TIP: also run the plot in viewing mode, enabled with tmap_mode("view")
}
# }