[R] regex find anything which is not a number

[John McKown]

See if the following will work for you:

grep('^-?[0-9]+([.]?[0-9]+)?$',myvector,perl=TRUE,invert=TRUE)

> myvector <- c("a3", "N.A", "1.2", "-3", "3-2", "2.")
> grep('^-?[0-9]+([.][0-9]+)?$',myvector,perl=TRUE,invert=TRUE)
[1] 1 2 5 6
>

The key is to match a number, and then invert the TRUE / FALSE (invert=TRUE).
^ == start of string
-? == 0 or 1 minus signs
[0-9]+ == one or more digits

optionally followed by the following via use of (...)?
[.] == an actual period. I tried to escape this, but it failed
[0-9]+ == followed by one or more digits

$ == followed by the end of the string.

so: optional minus, followed by one or more digits, optionally
followed by (a period with one or more ending digits).


On Wed, Mar 11, 2015 at 2:27 PM, Adrian Dușa <dusa.adrian at unibuc.ro> wrote:
> Hi everyone,
>
> I need a regular expression to find those positions in a character
> vector which contain something which is not a number (either positive
> or negative, having decimals or not).
>
> myvector <- c("a3", "N.A", "1.2", "-3", "3-2", "2.")
>
> In this vector, only positions 3 and 4 are numbers, the rest should be captured.
> So far I am able to detect anything which is not a number, excluding - and .
>
>> grep("[^-0-9.]", myvector)
> [1] 1 2
>
> I still need to capture positions 5 and 6, which in human language
> would mean to detect anything which contains a "-" or a "." anywhere
> else except at the beginning of a number.
>
> Thanks very much in advance,
> Adrian
>
>
> --
> Adrian Dusa
> University of Bucharest
> Romanian Social Data Archive
> Soseaua Panduri nr.90
> 050663 Bucharest sector 5
> Romania
>
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John McKown