thinPolys function

Thin a PolySet of Polygons

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

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.

Returns

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)
})