Append a Two-Column Matrix to a PolySet
Append a two-column matrix to a PolySet, assigning PID and
possibly SID values automatically or as specified in its
arguments.
appendPolys (polys, mat, PID = NULL, SID = NULL, isHole = FALSE)
If the PID argument is NULL, the appended polygon's
PID will be one greater than the maximum within polys
(if defined); otherwise, it will be 1.
If polys contains an SID column and the SID
argument equals NULL, this function uses the next available
SID for the corresponding PID.
If polys does not contain an SID column and the
caller passes an SID argument, all existing polygons will
receive an SID of 1. The new polygon's SID will
match the SID argument.
If isHole = TRUE, the polygon's POS values will
appropriately represent a hole (reverse order of POS).
If (PID, SID) already exists in the PolySet, the
function will issue a warning and duplicate those identifiers.
PolySet containing mat appended to polys. The
function retains attributes from polys.
Nicholas M. Boers, Associate Professor – Computer Science
MacEwan University, Edmonton AB
Last modified Rd: 2013-04-10
local(envir=.PBSmapEnv,expr={
#--- create two simple matrices
a <- matrix(data=c(0,0,1,0,1,1,0,1),ncol=2,byrow=TRUE);
b <- matrix(data=c(2,2,3,2,3,3,2,3), ncol=2,byrow=TRUE);
#--- build a PolySet from them
polys <- appendPolys(NULL, a);
polys <- appendPolys(polys, b);
#--- print the result
print (polys);
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