fixPOS function

Fix the POS Column of a PolySet

Fix the POS column of a PolySet by recalculating it using sequential integers.

fixPOS (polys, exteriorCCW = NA)

Arguments

• polys: PolySet to fix.
• exteriorCCW: Boolean value; if TRUE, orders exterior polygon vertices in a counter-clockwise direction. If FALSE, orders them in a clockwise direction. If NA, maintains their original order.

Details

This function recalculates the POS values of each (PID, SID) as either 1 to N or N to 1, depending on the order of POS (ascending or descending) in the input data. POS

values in the input must be properly ordered (ascending or descending), but they may contain fractional values. For example, POS = 2.5 might correspond to a point manually added between POS = 2 and POS = 3. If exteriorCCW = NA, all other columns remain unchanged. Otherwise, it orders the X and Y columns according to exteriorCCW.

Returns

PolySet with the same columns as the input, except for possible changes to the POS, X, and Y columns.

Author(s)

Nicholas M. Boers, Staff Software Engineer

Jobber, Edmonton AB

Last modified Rd: 2013-04-10

See Also

closePolys, fixBound, isConvex, isIntersecting, PolySet .

Examples

local(envir=.PBSmapEnv,expr={
  #--- create a PolySet with broken POS numbering
  polys <- data.frame(PID = c(rep(1, 10), rep(2, 10)),
    POS = c(seq(2, 10, length = 10), seq(10, 2, length = 10)),
    X = c(rep(1, 10), rep(1, 10)),
    Y = c(rep(1, 10), rep(1, 10)))
  #--- fix the POS numbering
  polys <- fixPOS(polys)
  #--- print the results
  print(polys)
})