/**
* A subgraph is calculated based on the participants collected based on the given node ids.
*
* @param array $ids
* The nodes interested in.
* @return DirectedGraph
* The subgraph with all participants
*/
public function subGraph($ids = array())
{
$g = new DirectedGraph();
$participants = $this->getParticipants($ids);
foreach ($participants as $id) {
$g->addNode($id);
// Only participating links are added.
$links = $this->getLinks($id);
if (is_array($links)) {
$g->addLinks($id, array_intersect($participants, $links));
}
}
return $g;
}
