calcConvexHull: Calculate Convex Hull for a Set of Points

In PBSmapping: Mapping Fisheries Data and Spatial Analysis Tools

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)

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.

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.

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)
})

PBSmapping documentation built on Sept. 30, 2024, 9:21 a.m.