Logical whether the graph is filled by
rows (otherwise by columns).
topdown
Logical whether the rows are filled top-down
or bottom-up.
force
Logical whether a graph that has already
a layout should be given the specified new layout.
Value
The graph with nodes placed according to the specified layout.
Details
If one of nrow or ncol is not given, an attempt is made to
infer it from the number of nodes of the graph and the other parameter.
If neither is given, the graph is placed as a circle.