stringr str_extract capture group capturing everything

Question

I\'m looking to extract the year from a string. This always comes after an \'X\' and before \".\" then a string of other characters.

Using stringr\'s

Answer 1

I believe the most idiomatic way is to use str_match:

str_match(string = 'X2015.XML.Outgoing.pounds..millions.',
          pattern = 'X(\\d{4})\\.')

Which returns the complete match followed by capture groups:

     [,1]     [,2]  
[1,] "X2015." "2015"

As such the following will do the trick:

str_match(string = 'X2015.XML.Outgoing.pounds..millions.',
          pattern = 'X(\\d{4})\\.')[2]