[R] how to extract characters from a character string

[Peter Dalgaard]

Weidong Gu wrote:
> Hi, I ran into a problem when I complied a dataset with UTM coordinates.
> For calculating distances between sites, I need to reformat the
> coordinates from, for example,
>
>  
>
> 32?35.421 N, to 35.421, i.e. I need to delete all digits before symbol ?
> and a space and N at the end of the string. What functions I should use?
>
>
>   
One of the regexpr family. Beware that this stuff can be quite 
maddening, but here's one option:

 > x <- "32?35.421 N"
 > sub("^.*\\?([.0-9]*) N$", "\\1", x)
[1] "35.421"

or less general but more straightforward:

 > sub(" N$", "", sub("^.*\\?", "", x))
[1] "35.421"


>
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>   


-- 
   O__  ---- Peter Dalgaard             Øster Farimagsgade 5, Entr.B
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