Returns \(I(p_2 \in N_{PE}(p_1,r,c))\) for points \(p_1\) and \(p_2\), that is, returns 1 if \(p_2\) is in \(N_{PE}(p_1,r,c)\),
returns 0 otherwise, where \(N_{PE}(x,r,c)\) is the PE proximity region for point \(x\) with expansion parameter \(r \ge 1\)
and centrality parameter \(c \in (0,1)\).
PE proximity region is constructed with respect to the
interval \((a,b)\). This function works whether \(p_1\) and \(p_2\) are inside or outside the interval int
.
Vertex regions for middle intervals are based on the center associated with the centrality parameter \(c \in (0,1)\).
If \(p_1\) and \(p_2\) are identical, then it returns 1 regardless of their locations
(i.e., loops are allowed in the digraph).
See also (ceyhan:metrika-2012;textualpcds).