triadCensus | R Documentation |
These functions provide some tools for finding triads in an undirected
graph. A triad is a clique of size 3. The function triadCensus
returns a list of all triads.
triadCensus(graph)
isTriad(x, y, z, elz, ely)
reduce2Degreek(graph, k)
enumPairs(iVec)
graph |
An instance of the |
k |
An integer indicating the minimum degree wanted. |
x |
A node |
y |
A node |
z |
A node |
elz |
The edgelist for |
ely |
The edgelist for |
iVec |
A vector of unique values |
enumPairs
takes a vector as input and returns a list of length
choose(length(iVec),2)/2
containing all unordered pairs of
elements.
isTriad
takes three nodes as arguments. It is already known
that x
has edges to both y
and z
and we want to
determine whether these are reciprocated. This is determined by
examining elz
for both x
and y
and then examining
ely
for both x
and z
.
reduce2Degreek
is a function that takes an undirected graph as
input and removes all nodes of degree less than k
. This process
is iterated until there are no nodes left (an error is thrown) or all
nodes remaining have degree at least k
. The resultant subgraph
is returned. It is used here because to be in a triad all nodes must
have degree 2 or more.
triadCensus
makes use of the helper functions described above
and finds all triads in the graph.
A list where each element is a triple indicating the members of the triad. Order is not important and all triads are reported in alphabetic order.
See the graph package, RBGL and Rgraphviz for more details and alternatives.
R. Gentleman
##---- Should be DIRECTLY executable !! ----
##-- ==> Define data, use random,
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