[R] trouble automating formula edits when log or * are present; update trouble

[Bert Gunter]

Paul et. al:

I think Gabor's incantation qualifies as my desired alternative to
eval(parse())). It is, unfortunately, rather tricky, imo.

However, the objection you raise to the gsub(deparse()) solution is
easily overcome through the use of an appopriate regex: e.g.:

 gsub("\\<x\\>","log(x)","x+xc+cx")
[1] "log(x)+xc+cx"

See the ?regex documentation on \< and \> . I believe this allows this
simple approach to handle all cases -- am I wrong about this?

Incidentally, I need to note that I was **wrong** in my previous statement that
formula(lm(y!x1))  does not work. It works fine, as there is a formula
method for (g)lm . I should look before I leap.

-- Bert




On Tue, May 29, 2012 at 10:41 AM, Paul Johnson <pauljohn32 at gmail.com> wrote:
>>>
>>
>> Try substitute:
>>
>>> do.call("substitute", list(newFmla, setNames(list(as.name("x1c")), "x1")))
>> y ~ log(x1c) + x2 * x3
>>
> Damn. That's pretty. I'd say "setNames" a magic bullet too.
>
> Thanks very much.
>
> The approach suggested by Michael and Bert has the little shortcoming
> that grepping for "x1" also picks up similarly named variables like
> "x1new" and "x1old".  I've not yet found a similar downside with
> Gabor's method.
>
> pj
>>
>> --
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>
>
>
> --
> Paul E. Johnson
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>
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-- 

Bert Gunter
Genentech Nonclinical Biostatistics

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