Determine if a graph has directed or undirected edges
确定如果有图有向或无向边
译者:生物统计家园网 机器人LoveR
描述----------Description----------
The edges of a graph-class object are either directed or undirected. This function returns TRUE if the edges are directed and FALSE otherwise.
graph-class对象的边缘向或无向。这个函数返回TRUE如果边缘定向FALSE否则。