Test if a directed graph is cyclic

Implements Kahn's algorithm to detect cycles in a directed graph.

Usage

is_cyclic(df)

Arguments

df

A data.frame with columns from and to.

Value

Logical. TRUE if the graph contains at least one cycle.

Examples

df <- data.frame(from=c("A","B"), to=c("B","A"))
is_cyclic(df)
#> [1] TRUE