Weak components join nodes linked by edges in either direction; strong
components (Tarjan's algorithm, without recursion) join nodes that
reach each other along the edges' directions. Undirected, the two
coincide. Components are numbered 1, 2, ... in the order of their first
node. Graph rules as in ntdeg().
Usage
ntcmp(from, to, nodes = NULL, dir = FALSE)
Arguments
- from, to
Labels of the two ends of each edge: vectors of the same
length (zero when nodes gives every node) with no missing values.
- nodes
NULL, or every node's label once: the node order of the
results and the way to include isolated nodes.
- dir
TRUE for a directed graph (from sends a tie to to).
Value
A data frame: node, weak, strong.
References
Tarjan, R. (1972). Depth-first search and linear graph
algorithms. SIAM Journal on Computing, 1(2), 146-160.
doi:10.1137/0201010
Examples
ntcmp(c("a", "b", "c", "x"), c("b", "c", "a", "y"), dir = TRUE)
#> node weak strong
#> 1 a 1 1
#> 2 b 1 1
#> 3 c 1 1
#> 4 x 2 2
#> 5 y 2 3
