R: Calculation of network or graph statistics

summary.statistics {ergm} | R Documentation

## Calculation of network or graph statistics

### Description

Used to calculate the specified statistics for an observed network if its argument is a formula for an `ergm`. See `ergm-terms` for more information on the statistics that may be specified.

### Usage

    ## Default S3 method:
    summary.statistics(object, response=NULL, ..., basis=NULL)
    ## S3 method for class 'matrix'
    summary.statistics(object, response=NULL, ..., basis=NULL)
    ## S3 method for class 'network'
    summary.statistics(object, response=NULL, ..., basis=NULL)
    ## S3 method for class 'network.list'
    summary.statistics(object, response=NULL, ..., basis=NULL)
    ## S3 method for class 'formula'
    summary.statistics(object, ..., basis=NULL)
    ## S3 method for class 'ergm'
    summary.statistics(object, ..., basis=NULL)

### Arguments

`object` | Either an R `formula` object (see above) or an `ergm` model object. In the latter case, `summary.statistics` is called for the `object$formula` object. In the former case, `object` is of the form `y ~ <model terms>`, where `y` is a `network` object or a matrix that can be coerced to a `network` object. For the details on the possible `<model terms>`, see `ergm-terms`. To create a `network` object in R, use the `network()` function, then add nodal attributes to it using the `%v%` operator if necessary.
`response` | Name of the edge attribute whose value is to be modeled. Defaults to `NULL` for simple presence or absence, modeled via binary ERGM terms. Passing anything but `NULL` uses valued ERGM terms.

`basis` | An optional `network` object relative to which the global statistics should be calculated.
`...` | further arguments passed to or used by methods.

### Details

If `object` is of class `formula`, then `summary` may be used in lieu of `summary.statistics` because `summary.formula` calls the `summary.statistics` function. The function actually cumulates the change statistics when removing edges from the observed network one by one until the empty network results. Since each model term has a prespecified value (zero by default) for the corresponding statistic(s) on an empty network, these change statistics give the absolute statistics on the original network.

`summary.formula` for networks understands the `lasttoggle` "API".

### Value

A vector of statistics measured on the network.

### See Also

ergm, network, ergm-terms

### Examples

    #
    # Lets look at the Florentine marriage data
    #
    data(florentine)
    #
    # test the summary.statistics function
    #
    summary(flomarriage ~ edges + kstar(2))
    m <- as.matrix(flomarriage)
    summary(m ~ edges)  # twice as large as it should be
    summary(m ~ edges, directed=FALSE) # Now it's correct

[Package ergm version 3.8.0 Index]