[R] extracting text contained in brackets ("[ ... ]") from a character string?

[Gabor Grothendieck]

If you know its of the form testdata[3] then this is sufficient

  x <- c("testdata[3]", "testdata[-4]", "testdata[-4g]")
  gsub(".*\\[|\\]", "", x)  # c("3", "-4", "-4g")

Here is a somewhat more general solution:

  library(gsubfn)
  x <- c("a[b]c[d]d", "[a]b")
  strapply(x, "\\[([^]]*)\\]", back = -1)   # list(c("b", "d"), "a")

On 5/13/07, new ruser <newruser at yahoo.com> wrote:
> I have a text string that contains text within two brackets.
>
> e.g. "testdata[3]" "testdata[-4]", "testdata[-4g]",
>
> I wish to "extract" the string enclosed in brackets?
>
> What is a good way to do this?
>
> e.g.
>
> fun(testdata[3]) = '3'
>
> fun(testdata[-4g]) = '-4g'
>
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