Specifies nodes to be used as the center of the layout and the root of the generated spanning tree.
- As a graph attribute, this gives the name of the node.
- As a node attribute, it specifies that the node should be used as a central node.
root will actually be the central node. In
block containing the node will be central in the drawing of its connected
component. If not defined,
twopi will pick a most central node, and
will pick a random node.
If the root attribute is defined as the empty string,
twopi will reset it to
name of the node picked as the root node.
twopi, it is possible to have multiple roots, presumably one for each
component. If more than one node in a component is marked as the
twopi will pick one.