update.formula and backticked colons

-----Original Message-----
From: William Dunlap 
Sent: Friday, July 31, 2009 10:15 AM
To: 'Sundar Dorai-Raj'; r-devel at stat.math.ethz.ch
Subject: RE: [Rd] update.formula and backticked colons

-----Original Message-----
From: r-devel-bounces at r-project.org 
[mailto:r-devel-bounces at r-project.org] On Behalf Of Sundar Dorai-Raj
Sent: Thursday, July 30, 2009 2:28 PM
To: r-devel at stat.math.ethz.ch
Subject: [Rd] update.formula and backticked colons

I just noticed the following in update.formula and I'm wondering if
this behavior is the intention of the developers. Here's an example:

update(`a: b` ~ x, ~ . + y)

Note now that the response has no backticks and is 

interpreted as a:b

(i.e. ":" is now an operator). This is because in update.formula the
call to terms.formula uses simplify = TRUE. I'm working 

with data that

has a lot of colons in their names and for reporting 

purposes I don't

want to use make.names to avoid this situation. I do have a solution
which simply avoids using update.formula, but I wonder if the
developers would consider removing the "simplify" argument and allow
it to be passed through "...", which is currently ignored by
update.formula. Alternatively, add a simplify=TRUE to the
update.formula call, which can manually be set to FALSE by the user.

I would love to hear any comments or criticisms of my findings.

Thanks,

--sundar

It would be nice to get right of the deparse/parse cycle in 
terms.formula,
since that often causes problems.  However, I think that 
adding backticks=TRUE

to terms.formula:fixFormulaObject's call to 
deparse(form[[2L]])  would fix the 
immediate problem.  (I haven't spent much time looking for 
bad side effects
of this change to terms.formula, which gets called in a lot 
of other situations.)

Bill Dunlap
TIBCO Software Inc - Spotfire Division
wdunlap tibco.com