> On Aug 2, 2016, at 11:46 AM, Dennis Fisher <fis...@plessthan.com> wrote:
>
> R 3.3.1
> OS X
>
> Colleagues,
>
> I have encountered an unexpected regex problem
>
> I have read an Excel file into R using the readxl package. Columns names are:
>
> COLNAMES <- c("Study ID", "Test and Biological Matrix", "Subject No. ",
> "Collection Date",
> "Collection Time", "Scheduled Time Point", "Concentration", "Concentration
> Units",
> "LLOQ", "ULOQ", "Comment”)
>
> As you can see, there is a trailing space in “Subject No. “. I would like to
> delete that space. The following works:
> sub(“ $”, “”, COLNAMES)
> However, I would like a more general approach that removes any trailing
> whitespace.
>
> I tried variations such as:
> sub("[:blank:]$", "", COLNAMES)
> (also, without the $ and ‘space' instead of ‘blank') without success — to my
> surprise, characters other than the trailing space were deleted but the
> trailing space remained.
>
> Guidance on the correct syntax would be appreciated.
>
> Dennis
Dennis,
There is actually an example in ?gsub:
## trim trailing white space
str <- "Now is the time "
sub(" +$", "", str) ## spaces only
The '+' sign will match the preceding space one or more times at the end of the
character string.
Note that as per ?regex, it is [:space:], not [:blank:] and the brackets need
to be doubled in the regex to define the enclosing character group. An example
would be:
sub("[[:space:]]+$", "", str) ## white space, POSIX-style
which is also in ?gsub.
Regards,
Marc Schwartz
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