R - Searching text with NEAR regex - r

Question

I have a vector containing text, broken up, like the following:
words = c("Lorem Ipsum is simply dummy text of the", "printing and typesetting industry. Lorem Ipsum has been the industrys
standard dummy text ever since the 1500s", "when an unknown printer took a galley of type and scrambled it to
make a type specimen book.", "It has survived not only five ,centuries, but also the leap into electronic")
I am using the following regex to find where the words "dummy" and "text" appear within 6 words of each other:
grep("\b(?:dummy\\W+(?:\\w+\\W+){1,6}?text|text\\W+(?:\\w+\\W+){1,6}?dummy)\b", words)
However its returning 0 despite there being 'dummy text' within the first index.
Any idea where I am going wrong?

Answer 1

The \b in "\b" matches a backspace char, you need to double escape the \b, \\b, to make it match a word boundary.
After fixing the typo, you need to pay attention to the limiting quantifiers. {1,6}? is a lazy quantifier matching one to six occurrences (as few as possible, but still as many as necessary to find a valid match) of the modified subpattern. It means there must be at least one word between dummy and text.
So, you need to use
pattern <- "\\b(?:dummy\\W+(?:\\w+\\W+){0,6}text|text\\W+(?:\\w+\\W+){0,6}dummy)\\b"
See the regex demo.
Details
\b - a word boundary
(?: - start of a non-capturing group
dummy - a dummy word
\W+ - one or more non-word chars
(?:\w+\W+){0,6} - zero to six occurrences of one or more word chars followed with one or more non-word chars
text - a text word
| - or
text - a text word
\W+ - one or more non-word chars
(?:\w+\W+){0,6} - zero to six occurrences of one or more word chars followed with one or more non-word chars
dummy - a dummy word
) - end of the non-capturing group
\b - a word boundary