[R] extract argument names

[Dimitris Rizopoulos]

one way seems to be the following:

a <- paste("qss(",paste("x",1:6,sep = "") ,", lambda =100)", sep = "")
all.vars(parse(text = a))


I hope it helps.

Best,
Dimitris


roger koenker wrote:
> I have a vector of character strings that look like R expressions:
> 
>  > a <- paste("qss(",paste("x",1:6,sep = "") ,", lambda =100)", sep = "")
>  > a
> [1] "qss(x1, lambda =100)" "qss(x2, lambda =100)" "qss(x3, lambda =100)"
> [4] "qss(x4, lambda =100)" "qss(x5, lambda =100)" "qss(x6, lambda =100)"
> 
> That I would like to operate on to obtain the names of the first 
> argument, i.e.
> 
>  > foo(a)
> [1] "x1" "x2" "x3" "x4" "x5" "x6"
> 
> I thought there was some simple idiom involving deparse, but it is eluding
> my searches.
> 
> 
> url:    www.econ.uiuc.edu/~roger            Roger Koenker
> email    rkoenker at uiuc.edu            Department of Economics
> vox:     217-333-4558                University of Illinois
> fax:       217-244-6678                Champaign, IL 61820
> 
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-- 
Dimitris Rizopoulos
Assistant Professor
Department of Biostatistics
Erasmus University Medical Center

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