[R] misbehavior with extract_numeric() from tidyr

[Hadley Wickham]

On Mon, Apr 20, 2015 at 1:57 PM, arnaud gaboury
<arnaud.gaboury at gmail.com> wrote:
> On Mon, Apr 20, 2015 at 6:09 PM, William Dunlap <wdunlap at tibco.com> wrote:
>
>> The hyphen without a following digit confuses tidyr::extract_numeric().
>> E.g.,
>>    > extract_numeric("23 ft-lbs")
>>    Warning message:
>>    In extract_numeric("23 ft-lbs") : NAs introduced by coercion
>>    [1] NA
>>    > extract_numeric("23 ft*lbs")
>>    [1] 23
>>
>
> See[0] for the reason on the minus in the regex. It is not a bug but a wish.
> I am honestly very surprised the maintainer decided to go with such a so
> simple solution for negative numbers.
>
> [0]https://github.com/hadley/tidyr/issues/20

Any heuristic is going to fail in some circumstances. If you want to
be sure it's doing what you want for your use case, write the regular
expression yourself.

Hadley

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