R: find largest common substring starting at the beginning

Question

I\'ve got 2 vectors:

word1 <- \"bestelling\"   
word2 <- \"bestelbon\"

Now I want to find the largest common substring that starts at the

Answer 1

fun <- function(words) {
  #extract substrings from length 1 to length of shortest word
  subs <- sapply(seq_len(min(nchar(words))), 
                 function(x, words) substring(words, 1, x), 
                 words=words)
  #max length for which substrings are equal
  neqal <- max(cumsum(apply(subs, 2, function(x) length(unique(x)) == 1L)))
  #return substring
  substring(words[1], 1, neqal)
}

words1 <- c("bestelling", "bestelbon")
fun(words1)
#[1] "bestel"

words2 <- c("bestelling", "stel")
fun(words2)
#[1] ""