[R] parse and eval character vector

[Rob Foxall]

That's great, thanks. I can live with the warnings!

Cheers,
Rob

On Tue, Aug 26, 2008 at 4:49 PM, ONKELINX, Thierry
<Thierry.ONKELINX at inbo.be> wrote:
>
> Just use as.numeric. Non numeric will be NA. So the solution of your
> problem is na.omit(as.numeric(temp1))
>
> HTH,
>
> Thierry
>
>
> ------------------------------------------------------------------------
> ----
> ir. Thierry Onkelinx
> Instituut voor natuur- en bosonderzoek / Research Institute for Nature
> and Forest
> Cel biometrie, methodologie en kwaliteitszorg / Section biometrics,
> methodology and quality assurance
> Gaverstraat 4
> 9500 Geraardsbergen
> Belgium
> tel. + 32 54/436 185
> Thierry.Onkelinx at inbo.be
> www.inbo.be
>
> To call in the statistician after the experiment is done may be no more
> than asking him to perform a post-mortem examination: he may be able to
> say what the experiment died of.
> ~ Sir Ronald Aylmer Fisher
>
> The plural of anecdote is not data.
> ~ Roger Brinner
>
> The combination of some data and an aching desire for an answer does not
> ensure that a reasonable answer can be extracted from a given body of
> data.
> ~ John Tukey
>
> -----Oorspronkelijk bericht-----
> Van: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org]
> Namens Rob Foxall
> Verzonden: dinsdag 26 augustus 2008 10:36
> Aan: r-help at r-project.org
> Onderwerp: [R] parse and eval character vector
>
> Dear R-help,
>
> I have a character vector, some elements will be numeric, some not,
> and some even empty. E.g.:
>
> temp1 <- c("abcd","  2 ","")
>
> I'm only interested in the numeric elements, the rest I can just throw
> away. It is easy enough to loop through the vector:
>
> temp <- try(eval(parse(text=temp1[1])), silent=TRUE); class(temp) #
> try-error
> temp <- try(eval(parse(text=temp1[2])), silent=TRUE); class(temp) #
> numeric
> temp <- try(eval(parse(text=temp1[3])), silent=TRUE); class(temp) # NULL
>
> and then throw away the non-numeric/NULL stuff. But, as this vector
> will be long, I would really like to speed things up by not using a
> loop, and I thought that "lapply" might do the trick. However:
>
> temp.fn <- function(x)
>  try(eval(parse(text=x)), silent=TRUE)
>
> temp2 <- lapply(temp1, FUN=temp.fn)
> class(temp2[2]) # list, for elements 1, 2, and 3
>
> and I don't know how to extract the numeric elements from here. So,
> can I either use lapply as above and somehow get the information I
> need out of "temp2" (I've tried using "unlist" but had no success), or
> is there some other function that I can apply to my character vector
> to avoid looping?
>
> Rob.
>
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