[R] Placeholders for String Operations

[Sarah Goslee]

Hi Simon,

What you need are regular expressions.

The help for gsub says this, but in such a way that if you didn't know
that's what you were looking for, you wouldn't learn it there:

     See the help pages on regular expression for details of the
     different types of regular expressions.

The See Also section has a better clue:

     regular expression (aka ‘regexp’) for the details of the pattern
     specification.

?regexp has a fairly terse explanation. I'd look at some of the many
guides to regular expressions online, and use ?regexp mainly for how
the R implementation differs from standard (mostly in the use of \).
The help page does list all the groups, which is what you wanted.

Sarah

On Wed, Sep 4, 2013 at 11:17 AM, Simon Pickert
<simon.pickert at t-online.de> wrote:
> Hi all,
>
> what are the placeholders for string operations/modifications? Is there a placeholder for numbers, which would allow me to easily replace all numbers in a string? Something like
>
> text1 <- c("this is a number 23%")
> text2 <- c("this is not a number bla%")
>
> newtext1 <- gsub(#%, [percentagevalue], text)
> newtext2 <- gsub(#%, [percentagevalue], text)
>
>
> newtext1  should be "this is a number [percentagevalue]"
> newtext2  should be "this is not a number 23%"
>
>
> I figured there is * ? . but I can't find a source that explains their use and lists other placeholders..
>
>
> Appreciate your help!
> Thanks
> Simon
-- 
Sarah Goslee
http://www.functionaldiversity.org