gridlines {sp}R Documentation

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

Description

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

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)

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

Details

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

Author(s)

Edzer J. Pebesma, e.pebesma@geo.uu.nl, using example code of Roger Bivand.

See Also

Function spTransform in package rgdal

Examples

data(meuse)
coordinates(meuse) = ~x+y
plot(meuse)
plot(gridlines(meuse), add=TRUE)
title("default gridlines within Meuse bounding box")
[Package sp version 0.9-12 Index]