NA and help page for "&" and "|"
Martin Maechler
Martin Maechler <maechler@stat.math.ethz.ch>
Tue, 20 Aug 2002 17:29:42 +0200
>>>>> "JonR" == Jonathan Rougier <J.C.Rougier@durham.ac.uk>
>>>>> on Tue, 20 Aug 2002 14:49:53 +0100 writes:
JonR> Hi everyone,
JonR> Can I suggest an addition to the help page for logical AND and OR,
JonR> indicating the behaviour of NA (which is currently not mentioned at
JonR> all). I think something simple like an extra paragraph in Details, eg
JonR> \code{NA} is a valid logical object. Where a component of \code{x} or
JonR> \code{y} is \code{NA}, the result will be \code{NA} if the outcome is
JonR> ambiguous. In other words \code{NA & TRUE} evaluates to \code{NA}, but
JonR> \code{NA & FALSE} evaluates to \code{FALSE}. See the examples below.
JonR> And so it might also be a good idea to add a truth-table to the
JonR> examples, eg
JonR> # construct truth table for logical &
JonR> x <- c(NA, FALSE, TRUE)
JonR> names(x) <- as.character(x)
JonR> outer(x, x, "&")
Thanks a lot, Jonathan, for the helpful suggestions.
I'm adding these to R-devel.
Martin
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