[R] Find and remove matching parentheses

[Gabor Grothendieck]

See:

http://finzi.psych.upenn.edu/R/Rhelp02a/archive/30590.html

On 4/2/06, Dieter Menne <dieter.menne at menne-biomed.de> wrote:
> To create a more end-user readable table captions for modeld, I would like
> to get rid of the I(...) construct in formulae ("what's the hell does the
> I(..) mean in the contrast table")
>
> Example:
>
> effect ~ I(sqrt(nitro))*treat + I(nitro^2)
>
> should giv
>
> effect ~ sqrt(nitro)*treat + nitro^2
>
> In know, this is a dumb model, just my test case. As far I remember, finding
> matching parentheses is nasty in regexp, so I resorted to a loop and
> counting opening/closing.
>
> Is there a more elegant solution?
>
> Dieter
>
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