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 RR be an endorelation with domain (X,X)(X, X) and consider elements xx and yy of XX. We say that xx is

minimal:

there is no yxy \ne x with yRxy R x.

a first element:

xRyx R y for all yxy \ne x.

a last element:

yRxy R x for all yxy \ne x.

maximal:

there is no yxy \ne x with xRyx 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 0.6-13 Index]