[R] UNIX-like "cut" command in R

[Gabor Grothendieck]

On Mon, May 2, 2011 at 10:32 PM, Mike Miller <mbmiller+l at gmail.com> wrote:
> On Tue, 3 May 2011, Andrew Robinson wrote:
>
>> try substr()
>
> OK.  Apparently, it allows things like this...
>
>> substr("abcdef",2,4)
>
> [1] "bcd"
>
> ...which is like this:
>
> echo "abcdef" | cut -c2-4
>
> But that doesn't use a delimiter, it only does character-based cutting, and
> it is very limited.  With "cut -c" I can do stuff this:
>
> echo "abcdefghijklmnopqrstuvwxyz" | cut -c-3,12-15,17-
>
> abclmnoqrstuvwxyz
>
> It extracts characters 1 to 3, 12 to 15 and 17 to the end.
>
> That was a great tip, though, because it led me to strsplit, which can do
> what I want, however somewhat awkwardly:
>
>> y <- "a b c d e f g h i j k l m n o p q r s t u v w x y z"
>> paste(unlist(strsplit(y, delim))[c(1:3,12:15,17:26)], collapse=delim)
>
> [1] "a b c l m n o q r s t u v w x y z"
>
> That gives me what I want, but it is still a little awkward.  I guess I
> don't quite get what I'm doing with lists.  I'm not clear on how this would
> work with a vector of strings.
>

Try this:

> read.fwf(textConnection("abcdefghijklmnopqrstuvwxyz"), widths = c(3, 8, 4, 1, 10), colClasses = c(NA, "NULL"))
   V1   V3         V5
1 abc lmno qrstuvwxyz



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