[R] regex sub with specified number of characters

[Johannes Radinger]

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)

Any suggestions?

Best regards,
Johannes

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