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This function tests whether the given graph is a DAG, a directed acyclic graph.

Usage

is_dag(graph)

Arguments

graph

The input graph. It may be undirected, in which case FALSE is reported.

Value

A logical vector of length one.

Details

is_dag() checks whether there is a directed cycle in the graph. If not, the graph is a DAG.

Author

Tamas Nepusz ntamas@gmail.com for the C code, Gabor Csardi csardi.gabor@gmail.com for the R interface.

Examples


g <- make_tree(10)
is_dag(g)
#> [1] TRUE
g2 <- g + edge(5, 1)
is_dag(g2)
#> [1] FALSE