map <- matrix (c ( " ", "X", " ", " ", "X", " ", "X", " ", "X", " ", "X", " ", " ", " ", " ", " ", " ", " ", " ", " "), nrow=5, ncol=4, byrow=TRUE) map find_distances(map,c(1,4)) find_distances(map,c(3,2)) find_distances(map,c(2,3))