Nothing

```
# Determine if a directed 0-1 matrix has a cycle
hasCycle = function(m, maxlen = NA) {
if(all(m == 0))
return(FALSE)
if(any(diag(m) == 1))
return(TRUE)
n = dim(m)[1]
if(is.na(maxlen)) {
rowRank = sum(.rowSums(m, n, n) > 0)
colRank = sum(.colSums(m, n, n) > 0)
maxlen = min(rowRank, colRank)
}
if(maxlen < 2)
return(FALSE)
mpow = m
for(i in 2:maxlen) {
mpow = mpow %*% m
if(any(diag(mpow) > 0))
return(TRUE)
}
FALSE
}
# All descendants of a node (or set of nodes) in a DAG
dagDescendants = function(adj, i, minDist = 1, maxDist = Inf) {
desc = if(minDist == 0) i else integer(0)
current = i # current set of individuals
dist = 0 # generation number
while(dist < maxDist && length(current) > 0) {
dist = dist + 1
# Next generation: All offspring of current
current = which(adj[current, , drop = FALSE], arr.ind = TRUE)[, 2]
# Add to storage if appropriate
if(dist >= minDist)
desc = c(desc, current)
}
# Return
as.integer(desc)
}
# Check connectedness of a directed adjacency matrix
isConnected = function(adj) {
n = dim(adj)[1]
# If size 1: connected
if(n == 1)
return(TRUE)
# Adj of undirected graph
a = adj | t.default(adj)
# Count in+out edges for each node
edgs = .rowSums(a, n, n)
if(any(edgs == 0))
return(FALSE)
nseq = seq_len(n)
getNeigh = function(ids) {
nids = length(ids)
if(nids == 1)
return(nseq[a[, ids]])
nseq[.rowSums(a[, ids], n, nids) > 0]
}
# Start at node with few edges
comp = integer()
new = which.min(edgs)
while(length(new) > 0) {
comp = c(comp, new)
neigh = getNeigh(new) # which(a[new, , drop = F], arr.ind = T)[, 2]
new = .mysetdiff(neigh, comp, makeUnique = FALSE)
}
# Connected iff all are included
length(comp) == n
}
```

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