nwissymmetric
Check whether a network is symmetric
Syntax
nwissymmetric
[netname]
Description
nwissymmetric simply checks if the underlying adjacency matrix of network netname is symmetric, regardless of whether the network is assigned to be directed or undirected (see nwname). An adjacency matrix M is symmetric when M_ij == M_ji. Returns r(issymmetric) in the return vector.
This command can be useful for programming, when one wants to detect if a network should be undirected.
For example, nwimport automatically checks if a network (e.g. Ucinet fullmatrix) is symmetric and if yes, imports the network as undirected.
Examples
. nwwebuse florentine
. nwissymmetric flomarriage
. return list
scalars:
r(issymmetric) = 1
Note: r(issymmetric) is a plain numeric 0/1 scalar - unlike the true/false string macros most other boolean-flag results in this group use (e.g. nwname’s r(directed)), since it is a computed test result rather than a stored network property.
Supported network types
Binary: yes. Directed: yes - this command’s entire purpose is checking whether a directed network’s matrix happens to be symmetric. Weighted: yes, checks exact value symmetry, not just tie presence. Signed: yes, a negative value is compared like any other. Two-mode: same as for the bipartite graph read as a one-mode network (valid; no mode-specific normalisation).
See also
nwcommands version 3.17.6, 9 November 2026 (check your installed version)