ergm_symmetrize {ergm}

Return a symmetrized version of a binary network

Description

Return a symmetrized version of a binary network

Usage

ergm_symmetrize(x, rule = c("weak", "strong", "upper", "lower"), ...)

## Default S3 method:
ergm_symmetrize(x, rule = c("weak", "strong", "upper", "lower"), ...)

## S3 method for class 'network'
ergm_symmetrize(x, rule = c("weak", "strong", "upper", "lower"), ...)

Arguments

x

an object representing a network.

rule

a string specifying how the network is to be symmetrized; see sna::symmetrize() for details; for the network method, it can also be a function or a list; see Details.

...

additional arguments to sna::symmetrize().

Details

The network method requires more flexibility, in order to specify how the edge attributes are handled. Therefore, rule can be one of the following types:

a character vector

The string is interpreted as in sna::symmetrize(). For edge attributes, "weak" takes the maximum value and "strong" takes the minimum value" for ordered attributes, and drops the unordered.

a function

The function is evaluated on a data.frame constructed by joining (via merge()) the edge tibble with all attributes and NA indicators with itself reversing tail and head columns, and appending original columns with ".th" and the reversed columns with ".ht". It is then evaluated for each attribute in turn, given two arguments: the data frame and the name of the attribute.

a list

The list must have exactly one unnamed element, and the remaining elements must be named with the names of edge attributes. The elements of the list are interpreted as above, allowing each edge attribute to be handled differently. Unnamed arguments are dropped.

Methods (by class)

• ergm_symmetrize(default): The default method, passing the input on to sna::symmetrize().

• ergm_symmetrize(network): A method for network objects, which preserves network and vertex attributes, and handles edge attributes.

Note

This was originally exported as a generic to overwrite sna::symmetrize(). By developer's request, it has been renamed; eventually, sna or network packages will export the generic instead.

Examples

data(sampson)
samplike[1,2] <- NA
samplike[4.1] <- NA
sm <- as.matrix(samplike)

tst <- function(x,y){
  mapply(identical, x, y)
}

stopifnot(all(tst(as.logical(as.matrix(ergm_symmetrize(samplike, "weak"))), sm | t(sm))),
          all(tst(as.logical(as.matrix(ergm_symmetrize(samplike, "strong"))), sm & t(sm))),
          all(tst(c(as.matrix(ergm_symmetrize(samplike, "upper"))),
                  sm[cbind(c(pmin(row(sm),col(sm))),c(pmax(row(sm),col(sm))))])),
          all(tst(c(as.matrix(ergm_symmetrize(samplike, "lower"))),
                  sm[cbind(c(pmax(row(sm),col(sm))),c(pmin(row(sm),col(sm))))])))