[R-sig-Geo] PBSmapping calcArea

Kenny Bell kmb56 at berkeley.edu
Thu Sep 25 00:00:27 CEST 2014

Hi all,

I am trying to use calcArea to get the areas of the following polygons at
the following link:


I use:

areaY <- calcArea(smallYPolySet, rollup = 2)

which gives the output:

> areaY
  PID SID        area
1   1   1  38.7704526
2   2   1 116.6810084
3   2   2   0.9844843

The second polygon has a hole which can be seen with:


However, the rollup = 2 option should see the hole and subtract the area
and return the difference, as I understand. The above shows they are
specified separately.

Can someone help me with any/all of:

1) working out whether the hole is identified in the smallYPolySet object
2) flagging an element of a polyset as a hole
2) automatically determining if a polygon is a hole

Any help would be very much appreciated!


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