calcConvexHull function

Calculate Convex Hull for a Set of Points

Calculate the convex hull for a set of points.

calcConvexHull(xydata, keepExtra=FALSE)
.closestPoint(pts, pt)

Arguments

• xydata: numeric -- data frame with columns 'X' and 'Y'

  containing spatial coordinates

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

• pts: numeric -- data frame with columns 'X' and 'Y'

• pt: numeric -- data frame with columns 'X' and 'Y' and ONE row

Details

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.

Returns

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

Auxiliary dot function '.closestPoint' returns a vector of length 'pts' where TRUE indicates that the point is closest to 'pt'. Returns several TRUE values when several points are equidistant.

Author(s)

Nicholas M. Boers, Software Engineer, Jobber, Edmonton AB

Maintainer: Rowan Haigh, Program Head -- Offshore Rockfish

Pacific Biological Station (PBS), Fisheries & Oceans Canada (DFO), Nanaimo BC

locus opus: Remote office, Vancouver BC

Last modified Rd: 2024-09-03

See Also

In package PBSmapping:

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)
})