In response to a query on Stack Overflow on March 10 2019 by Ankit, the
following function, FindCycles, was given:
## More efficient version
FindCycles = function(g) {
Cycles = NULL
for(v1 in V(g)) {
if(degree(g, v1, mode="in") == 0) { next }
GoodNeighbors = neighbors(g, v1, mode="out")
GoodNeighbors = GoodNeighbors[GoodNeighbors > v1]
for(v2 in GoodNeighbors) {
TempCyc = lapply(all_simple_paths(g, v2,v1, mode="out"), function(p)
c(v1,p))
TempCyc = TempCyc[which(sapply(TempCyc, length) > 3)]
###
TempCyc = TempCyc[sapply(TempCyc, min) == sapply(TempCyc, `[`, 1)]
Cycles = c(Cycles, TempCyc) }
}
Cycles
}
I am interested in finding cycles of any length, so that the line marked ###
should be removed.
The resultant code works for cycles of size at least two, but does not catch
singleton cycles.
Is there a simple fix?
(I wrote an obvious modification of the code above to search for just singleton
cycles, but it seems that there must be a simple tweak to the code above.)
Many thanks,
Simon
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