Calculate the Convex Hull for a Set of Points
Calculate the convex hull for a set of points.
calcConvexHull (xydata, keepExtra=FALSE)
xydata |
a data frame with columns |
keepExtra |
logical: if |
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.
PolySet with columns PID, POS, X, Y,
and additional columns in xydata if keepExtra=TRUE.
Nicholas M. Boers, Associate Professor – Computer Science
MacEwan University, Edmonton AB
Last modified Rd: 2013-04-10
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)
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