thinPolys: Thin a PolySet of Polygons

Description Usage Arguments Details Value Author(s) See Also Examples

Description

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

Usage

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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, Associate Professor – Computer Science
MacEwan University, Edmonton AB
Last modified Rd: 2013-04-10

See Also

thickenPolys.

Examples

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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 Jan. 15, 2021, 3:41 p.m.