[R] Regular expression to find value between brackets

[Erik Iverson]

Bart,

I'm hardly one of the lists regex gurus: but this can
get you started...

tests <- c("pH", "Assay (%)", "Impurity A(%)", "content (mg/ml)")

x <- regexpr("\\((.*)\\)", tests)
substr(tests, x + 1, x + attr(x, "match.length") - 2)


Bart Joosen wrote:
> Hi,
> 
> this should be an easy one, but I can't figure it out.
> I have a vector of tests, with their units between brackets (if they have
> units).
> eg tests <- c("pH", "Assay (%)", "Impurity A(%)", "content (mg/ml)")
> 
> Now I would like to hava a function where I use a test as input, and which
> returns the units
> like:
> f <- function (x) sub("\\)", "", sub("\\(", "",sub("[[:alnum:]]+","",x)))
> this should give "", "%", "%", "mg/ml", but it doesn't do the job quit well.
> 
> After searching in the manual, and on the help lists, I cant find the
> answer.
> 
> anyone?
> 
> Bart