R: Elements of Relation Domains

elements {relations} | R Documentation

## Elements of Relation Domains

### Description

Obtain elements of endorelation domains which have certain properties.

### Usage

    relation_elements(x, which, ...)

### Arguments

`x` | an endorelation.
`which` | a character string specifying the property to be tested for. Currently, one of `"minimal"`, `"first"`, `"last"`, or `"maximal"`, or a unique abbreviation thereof.
`...` | additional arguments to be employed in the property tests.

### Details

Let R be an endorelation with domain (X, X) and consider elements x and y of X. We say that x is

minimal:

  there is no y != x with y R x.

a first element:

  x R y for all y != x.

a last element:

  y R x for all y != x.

maximal:

  there is no y != x with x R y.

When computing the tests for the above properties, an additional `na.rm` argument can be given to control the handling of missing incidences. By default, these are treated as false, to the effect that they invalidate “for all” tests (corresponding to `na.rm = FALSE`) and pass the “there is no” tests (corresponding to `na.rm = TRUE`).

### Value

A set with the elements having the specified property.

[Package relations version 0.6-7 Index]