[R-sig-Geo] Detect islands (of more than 1 areas or polygons) into a cartography

[Marc Marí Dell'Olmo]

Dear all,

Anyone knows a function to detect if there are islands into a
cartography. I refer to islands with more than one area (or polygons).
In other words, I would like to detect how many connected components I
have in the graph.

On the other hand, I would like to know the “id” of the areas (or
polygons) for each island.

Note: I usually use the "readShapePoly " to open the cartography.

Thank you very much!
Marc