gridlines

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Percentile

Create N-S and E-W grid lines over a geographic region

Create N-S and E-W grid lines over a geographic region; gridat permits the construction of points and labels for non-projected grid annotation

Keywords
spatial
Usage
gridlines(x, easts = pretty(bbox(x)[1,]), norths = pretty(bbox(x)[2,]), ndiscr = 20) 
gridat(x, easts = pretty(bbox(x)[1,]), norths = pretty(bbox(x)[2,]), offset=0.5, side="WS")
Arguments
x
object deriving from class Spatial-class
easts
numeric; east-west values for vertical lines
norths
numeric; north-south values for horizontal lines
ndiscr
integer; number of points used to discretize the line, could be set to 2, unless the grid is (re)projected
offset
offset value to be returned, see text
side
default WS, if EN labels placed on the top and right borders
Value

  • gridlines returns an object of class SpatialLines-class, with lines as specified; the return object inherits the projection information of x; gridat returns a SpatialPointsDataFrame with points at the west and south ends of the grid lines created by gridlines, with degree labels

See Also

spTransform; llgridlines in rgdal (recent versions) for plotting long-lat grid over projected data

Aliases
  • gridlines
  • gridat
Examples
data(meuse)
coordinates(meuse) = ~x+y
plot(meuse)
plot(gridlines(meuse), add=TRUE)
title("default gridlines within Meuse bounding box")

if (require(rgdal)) {
proj4string(meuse) <- CRS("+init=epsg:28992")
meuse_ll <- spTransform(meuse, CRS("+proj=longlat +datum=WGS84"))
grd <- gridlines(meuse_ll)
grd_x <- spTransform(grd, CRS("+init=epsg:28992"))
plot(meuse)
plot(grd_x, add=TRUE, lty=2)
grdat_ll <- gridat(meuse_ll)
grdat_x <- spTransform(grdat_ll, CRS("+init=epsg:28992"))
text(coordinates(grdat_x), labels=parse(text=grdat_x$labels),
  pos=grdat_x$pos, offset=grdat_x$offset)
plot(meuse)
plot(grd_x, add=TRUE, lty=2)
grdat_ll <- gridat(meuse_ll, side="EN")
grdat_x <- spTransform(grdat_ll, CRS("+init=epsg:28992"))
text(coordinates(grdat_x), labels=parse(text=grdat_x$labels),
  pos=grdat_x$pos, offset=grdat_x$offset)
}
Documentation reproduced from package sp, version 0.9-94, License: GPL (>= 2)

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