mutual-ergmTerm-22863009: Mutuality

In ergm: Fit, Simulate and Diagnose Exponential-Family Models for Networks

Mutuality

Description

In binary ERGMs, equal to the number of pairs of actors i and j for which (i{\rightarrow}j) and (j{\rightarrow}i) both exist.

For valued ERGMs, equal to \sum_{i<j} m(y_{i,j},y_{j,i}) , where m is determined by form argument: "min" for \min(y_{i,j},y_{j,i}), "nabsdiff" for -|y_{i,j},y_{j,i}|, "product" for y_{i,j}y_{j,i}, and "geometric" for \sqrt{y_{i,j}}\sqrt{y_{j,i}}. See \insertCiteKr12e;textualergm for a discussion of these statistics. form="threshold" simply computes the binary mutuality after thresholding at threshold.

This term can only be used with directed networks.

Usage

# binary: mutual(same=NULL, by=NULL, diff=FALSE, keep=NULL, levels=NULL)

# valued: mutual(form="min",threshold=0)

Arguments

same	if the optional argument is passed (see Specifying Vertex attributes and Levels (?nodal_attributes) for details), only mutual pairs that match on the attribute are counted; separate counts for each unique matching value can be obtained by using diff=TRUE with same. Only one of same or by may be used. If both parameters are used, by is ignored. This paramer is affected by diff.
by	if the optional argument is passed (see Specifying Vertex attributes and Levels (?nodal_attributes) for details), then each node is counted separately for each mutual pair in which it occurs and the counts are tabulated by unique values of the attribute. This means that the sum of the mutual statistics when by is used will equal twice the standard mutual statistic. Only one of same or by may be used. If both parameters are used, by is ignored. This paramer is not affected by diff.
keep	deprecated
levels	which statistics should be kept whenever the mutual term would ordinarily result in multiple statistics. (See Specifying Vertex attributes and Levels (?nodal_attributes) for details.)
form, threshold	variant to be used in the valued case.

Note

The argument keep is retained for backwards compatibility and may be removed in a future version. When both keep and levels are passed, levels overrides keep. See nodal_attributes.

See Also

ergmTerm for index of model terms currently visible to the package.

\Sexpr[results=rd,stage=render]{ergm:::.formatTermKeywords("ergmTerm", "mutual", "subsection")}

ergm documentation built on Feb. 18, 2026, 1:06 a.m.