str_dup() duplicates the characters within a string, e.g.
str_dup("xy", 3) returns "xyxyxy".
Examples
fruit <- c("apple", "pear", "banana")
str_dup(fruit, 2)
#> [1] "appleapple" "pearpear" "bananabanana"
str_dup(fruit, 2, sep = " ")
#> [1] "apple apple" "pear pear" "banana banana"
str_dup(fruit, 1:3)
#> [1] "apple" "pearpear" "bananabananabanana"
str_c("ba", str_dup("na", 0:5))
#> [1] "ba" "bana" "banana" "bananana"
#> [5] "banananana" "bananananana"
