PBSmapping (version 2.74.1)

calcConvexHull: Calculate Convex Hull for a Set of Points

Description

Calculate the convex hull for a set of points.

Usage

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

Value

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.

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

Author

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

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.

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)
})