[R] Dealing with parentheses within variable names

[William Dunlap]

> R shouldn't have trouble with names like that

You will need to enclose the names with backquotes, `odd Name (parens)`, when using them
in expressions.  E.g.,

  > d <- data.frame(`P/E`=c(20,25,22), `% Growth`=c(2.4, 2.8, 5.0), `+-`=c(TRUE,TRUE,FALSE), check.names=FALSE)
  > # In the former you could use "P/E"=, but `P/E` works.  check.names=FALSE stops name mangling
  > d
    P/E % Growth    +-
  1  20      2.4  TRUE
  2  25      2.8  TRUE
  3  22      5.0 FALSE
  > # in the next `% Growth` is essential
  > lm(`% Growth` ~ ., data=d)
  
  Call:
  lm(formula = `% Growth` ~ ., data = d)
  
  Coefficients:
  (Intercept)        `P/E`     `+-`TRUE
         3.24         0.08        -2.44

> If you find functions in base R that object to those names, I think we'd
> like to fix them.

A core R function that fails with odd names is reformulate():
   > reformulate(c("P/E", "% Growth"), response="+-")
   Error in parse(text = termtext) : <text>:1:16: unexpected input
   1: response ~ P/E+% Growth
                    ^
It works you you add the `` inside the "" (for the termlabels, but not needed
for the response argument):
  > reformulate(c("`P/E`", "`% Growth`"), response="+-")
  `+-` ~ `P/E` + `% Growth`

Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com


> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On Behalf
> Of Duncan Murdoch
> Sent: Thursday, February 28, 2013 1:46 PM
> To: Jesus Munoz Serrano
> Cc: r-help at r-project.org
> Subject: Re: [R] Dealing with parentheses within variable names
> 
> On 28/02/2013 11:08 AM, Jesus Munoz Serrano wrote:
> > Dear all
> >
> > I'm having some problems with a data set that has parenthesis within the variable
> names. A example of this kind of variable names is the following:
> >
> > 				fBodyGyroskewness()Z
> >
> > The case is that R is having a lot of troubles to identify the variable (probably it does
> understand it like a function). I've tried (among other things) to remove the parenthesis
> from the name using the following command:
> >
> > 				names(dataFrame) <- sub("()","", names(dataFrame))
> >
> > but It didn't work.  Sorry if it's a silly issue but I would really appreciate if anybody could
> help me. Thank you very much.
> R shouldn't have trouble with names like that, but a lot of packages
> will (e.g. the ones that construct strings and call parse() on them).
> If you find functions in base R that object to those names, I think we'd
> like to fix them.  If the functions are in contributed packages, your
> mileage may vary.
> 
> Duncan Murdoch
> 
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