Obtain elements of endorelation domains which have certain properties.
relation_elements(x, which, ...)A set with the elements having the specified property.
an endorelation.
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.
Let \(R\) be an endorelation with domain \((X, X)\) and consider elements \(x\) and \(y\) of \(X\). We say that \(x\) is
there is no \(y \ne x\) with \(y R x\).
\(x R y\) for all \(y \ne x\).
\(y R x\) for all \(y \ne x\).
there is no \(y \ne x\) 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).