convertGroupPair function

Convert group pair $(q,l)$

Gives the index in $1, \ldots, Q^2$ (directed) or $1, \ldots, Q*(Q+1)/2$ (undirected) that corresponds to group pair $(q,l)$. Works also for vectors of indices $q$ and $l$.

convertGroupPair(q, l, Q, directed = TRUE)

Arguments

• q: Group index $q$
• l: Group index $l$
• Q: Total number of groups $Q$
• directed: Boolean for directed (TRUE) or undirected (FALSE) case

Returns

Index corresponding to the group pair $(q,l)$

Details

Relations between groups $(q,l)$ are stored in vectors, whose indexes depend on whether the graph is directed or undirected.

• Directed case :: * The $(q,l)$ group pair is converted into the index $(q-1)*Q+l$
• Undirected case :: * The $(q,l)$ group pair with $q\<=l$ is converted into the index $(2*Q-q+2)*(q-1)/2 +l-q+1$

Examples

# Convert the group pair (3,2) into an index, where the total number of group is 3,
# for directed and undirected graph

q <- 3
l <- 2
Q <- 3

directedIndex <- convertGroupPair(q,l,Q)
undirectedIndex <- convertGroupPair(q,l,Q, FALSE)