x <- c("popular", "popularity", "popularize", "popularise",
"Popular", "Population", "repopulate", "reproduce",
"happy family", "happier\tfamily", " happy family", "P6dn")
grep(pattern = 'pop', x) #1
[1] 1 2 3 4 7
[1] 1 2 3 4
[1] 3 4
[1] 3 4 7
[1] 3 4 7 8 10
[1] 6