In an Rweave tutorial written for possibly naive R users, I felt it
necessary to explain why
table() had to be used inside with(), whereas other tools like xtabs()
had a data= argument.
with() is quite nice for such cases, but it seems an unnecessary thing
to learn right off.
Before I turn this question into a request for R-devel, is there any
inherent reason why it might be
hard to add a data= argument to table()? I've looked at the code, but
am not enlightened
on this question.
\emph{Example}: Convert the \code{Arthritis} data in case form to a
3-way table of
\code{Treatment} $\times$ \code{Sex} $\times$ \code{Improved}.%
\footnote{
Unfortunately, \codefun{table} does not allow a \code{data} argument to
provide
an environment in which the table variables are to be found. In the
examples in \secref{sec:table} I used \code{attach(mydata)} for this
purpose,
but \codefun{attach} leaves the variables in the global environment,
while \codefun{with} just evaluates the \codefun{table} expression in a
temporary environment of the data.
}
<<convert-ex2,results=verbatim>>=
Art.tab <-with(Arthritis, table(Treatment, Sex, Improved))
str(Art.tab)
ftable(Art.tab)
@