v(...)
u(...)
d(...)
r(...)
v
and strictly positive integers for u
,d
and r
)v
returns an object of class "vertexSet"
.
Function u
returns an object of class "undirectedEdge"
.
Both functions d
and r
return an object of class "directedEdge"
.
d
builds a directed edge from tail to head,
function r
builds a directed edge from head to tail.vertexSet-class
,
undirectedEdge-class
and
directedEdge-class
.