R Graphical Manual

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Last data update: 2014.03.03

R: Add vertices to a polygon or line

makePoly

R Documentation

Add vertices to a polygon or line

Description

Make a polygon or line by adding intermedate points (vertices) on the great circles inbetween the points supplied. This can be relevant when vertices are relatively far apart. It can make the shape of the object to be accurate, when plotted on a plane. makePoly will also close the polygon if needed.

Usage

makePoly(p, interval=10000, r=6378137, sp=FALSE)
makeLine(p, interval=10000, r=6378137, sp=FALSE)

Arguments

`p`	a 2-column matrix (longitude/latitude) or a SpatialPolygons or SpatialLines object
`interval`	maximum interval of points, in units of r
`r`	radius of the earth; default = 6378137
`sp`	Logical. If `TRUE`, a SpatialPolygons object is retunred (depends on the 'sp' package)

Value

A matrix

Author(s)

Robert J. Hijmans

Examples

pol <- rbind(c(-180,-20), c(-160,5), c(-60, 0), c(-160,-60), c(-180,-20))
plot(pol)
lines(pol, col='red', lwd=3)
pol2 = makePoly(pol, interval=100000)
lines(pol2, col='blue', lwd=2)