This script calculates and displays the similarity between two myanimelist.net users using the scores given by them to their common series. To see the similarity go to http://myanimelist.net/sharedanime.php?u1=user1... where user1 and user2 are the usernames of the two users. The similarity is calculated by calculating the Carl Pearson's Correlation Coefficient between the scores of the two users.
The similarity value can be in the range of -100% to +100%. A value of 0% means that the users are indifferent of each other (that is their scores are such that they cancel out). A negative value means that the users are dissimilar and a positive value indicates similarity. -100% means totally dissimilar (first user equally hates the entry that second user likes) and +100% means totally similar (both user equally like an entry).
For reference see: http://en.wikipedia.org/wiki/Correlation