The Canberra distance between x and y. For example, between vectors
(1,2,0) and (0,1,1), for position 1 we have (1-0)/1, for position 2 we have
(2-1)/3, and for position 3 we have abs(0-1)/1, added together this results
in 2 1/3, or 2.33. Note that a text distance of zero indicates that the
two vectors are equal, while a text distance of 1 indicates that they have
no terms in common.