For the special tt mark in a formula, the answer is "mine". Other than that coxph handles
formulas in a completely standard way.
I don't see any other solution, frankly, unless I want to get really complex. If formulas
were not handled in an odd way, I'd simply add tt() to my namespace, not export it, and
coxph would get my function by preference. I had to engage in a little more trickery to
get this behavior, but that is somewhat beside the point.
The key issue is actually the same one addressed by namespaces: when my function sees tt()
in a formula, how does it decide whether to use its own function ("tt" is special, and
documented as so), or believe that some other version is avaialable and should be used?
If there is a tt() in the working directory? In an attached library()? In a directory on
the search list (but ignore libraries)? An attached "esp" library that reads the user's
mind?
Terry T.
On 01/29/2014 09:48 AM, Duncan Murdoch wrote:
I'm not familiar with how coxph handles formulas. Can a user put f(x) into a
formula,
where f is a user-defined function? If a user defines a tt function, will
coxph use
theirs, or yours?
I'd say the answers for situations like this should be "yes" and "theirs", but
that's not
true of my tables package, where answers to the corresponding questions would be
"yes" and
"mine".
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