thinPolys: Thin a PolySet of Polygons

In PBSmapping: Mapping Fisheries Data and Spatial Analysis Tools

Thin a PolySet of Polygons

Description

Thin a PolySet, where each unique (PID, SID) describes a polygon.

Usage

thinPolys (polys, tol = 1, filter = 3)

Arguments

polys	PolySet to thin.
tol	tolerance (in kilometres when proj is "LL" and "UTM"; otherwise, same units as polys).
filter	minimum number of vertices per result polygon.

Details

This function executes the Douglas-Peuker line simplification algorithm on each polygon within polys.

Value

PolySet containing the thinned data. The function recalculates the POS values for each polygon.

Author(s)

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

See Also

thickenPolys.

Examples

local(envir=.PBSmapEnv,expr={
  oldpar = par(no.readonly=TRUE)
  #--- load the data (if using R)
  if (!is.null(version$language) && (version$language=="R"))
    data(nepacLL,envir=.PBSmapEnv)
  #--- plot a thinned version of Vancouver Island (3 km tolerance)
  plotMap(thinPolys(nepacLL[nepacLL$PID == 33, ], tol = 3))
  #--- add the original Vancouver Island in a different line type to
  #--- emphasize the difference
  addPolys(nepacLL[nepacLL$PID == 33, ], border=2, lty=8, density=0)
  par(oldpar)
})

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