ode>data</code>) should be still considered connected if they are allocated to
different zones. The cell values along the diagonal
of the matrix indicate if planning units should be subject to
contiguity constraints when they are allocated to a given zone. Note
arguments to <code>zones</code> must be symmetric, and that a row or column has
a value of one then the diagonal element for that row or column must also
have a value of one. If the connection scheme between different zones
should differ among the fe