[R] regex sub with specified number of characters

[David Winsemius]

On Oct 6, 2015, at 7:38 AM, Johannes Radinger wrote:

> Hi
> 
> I'd like to remove a leading "3" if my number is 7 digits long, if it is
> only 6 I don't want to anything.
> I think this should be possible with a 1-liner using sub() but I am not
> sure how to define the number of characters following the leading one.
> 
> For example my vector:
> 
> a <- c(3593857,384723,4395843,3398374)
> 
> with sub("^3","",a) I also remove the leading from the second element which
> is only 6 digits long. So how to restrict that using sub? The final result
> should be
> 
> a <- c(593857,384723,4395843,398374)

Use a wild-card capture class of the correct length:

> sub("^3(.{6})$", "\\1", a)
[1] "593857"  "384723"  "4395843" "398374" 

> 
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-- 

David Winsemius
Alameda, CA, USA