calcConvexHull {PBSmapping}

Calculate the Convex Hull for a Set of Points

Description

Calculate the convex hull for a set of points.

Usage

calcConvexHull (xydata, keepExtra=FALSE)

Arguments

xydata

a data frame with columns X and Y containing spatial coordinates.

keepExtra

logical: if TRUE, retain any additional columns from the input data frame xydata.

Details

This routine uses the function chull() in the package grDevices. By default, it ignores all columns other than X and Y; however, the user can choose to retain additional columns in xydata by specifying keepExtra=TRUE.

Value

PolySet with columns PID, POS, X, Y, and additional columns in xydata if keepExtra=TRUE.

Author(s)

Nicholas M. Boers, Staff Software Engineer
Jobber, Edmonton AB
Last modified Rd: 2013-04-10

See Also

addPoints, addPolys, calcArea, calcCentroid, calcMidRange, calcSummary, locateEvents, plotMap, plotPoints, plotPolys.

Examples

local(envir=.PBSmapEnv,expr={
  oldpar = par(no.readonly=TRUE)
  data(surveyData,envir=.PBSmapEnv)
  #--- plot the convex hull, and then plot the points
  plotMap(calcConvexHull(surveyData),col="moccasin")
  addPoints(surveyData,col="blue",pch=17,cex=.6)
  par(oldpar)
})