Convert a Directed Network to Undirected

Collapses each pair of opposite arcs into one undirected edge, as igraph::as_undirected() and tidygraph's to_undirected() do.

Usage

to_undirected(
  x,
  method = c("max", "sum", "mean", "min", "mutual"),
  keep_format = FALSE,
  directed = NULL
)

Arguments

x

Network input.

method

How to combine w[i, j] and w[j, i]. One of "max" (default), "sum", "mean", "min" or "mutual". The first four combine the two weights when both arcs exist, and an arc without a reverse arc keeps its own weight. "mutual" keeps only reciprocated pairs, at the smaller of the two weights.

keep_format

Logical. If TRUE, a matrix, igraph, statnet network or tna input is returned in its own format. An edge-list data frame or a qgraph object is returned as a cograph_network with a cograph_no_format_roundtrip warning. Default FALSE returns a cograph_network.

directed

Logical or NULL. Directedness used to read the input. NULL (default) detects it from the input.

Value

An undirected cograph_network, or the input format when keep_format = TRUE. Self-loops keep their weight. A weight of zero means no edge, so a pair whose combined weight is exactly zero is dropped. Under method = "mutual" this applies to every unreciprocated arc, and under "sum" to a pair of opposite weights that cancel. Dropped edges raise a cograph_edges_dropped warning.

See also

to_directed, symmetrize

Examples

to_undirected(regulation_net, method = "sum")
#> Cograph network: 10 nodes, 27 edges ( undirected )
#> Source: matrix 
#>   Nodes (10): Explore, Plan, Monitor, Adapt, Reflect, Discuss, ... +4 more
#>   Edges: 27 / 45 (density: 60.0%)
#>   Weights: [0.070, 0.570]  |  mean: 0.295
#>   Strongest edges:
#>     Plan -- Share  0.570
#>     Monitor -- Create  0.540
#>     Plan -- Evaluate  0.490
#>     Monitor -- Share  0.490
#>     Adapt -- Evaluate  0.430
#> Layout: none 
#>   Use as.data.frame() for the edge table, as.data.frame(what = "nodes") for the nodes.