Description Usage Arguments Value Author(s) See Also Examples
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
1 2 3 4 |
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 |
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
Edzer Pebesma, edzer.pebesma@uni-muenster.de, using example code of Roger Bivand.
spTransform; llgridlines in rgdal
(recent versions) for plotting long-lat grid over projected data
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 | 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)
}
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