The command is.connected(X) returns TRUE if the object
X consists of a single, topologically-connected piece,
and returns FALSE if X consists of several pieces
which are not joined together.
The function is.connected is generic.
The default method is.connected.default
works for many classes of objects, including windows (class "owin")
and images (class "im").
There is
a method for point patterns, described in is.connected.ppp.