Hi all,
I'm new to the community and Mahout. Happy to be here. :-)
I have the following problem that I'm having difficulty with. I've setup an
instance on Amazon with Mahout and can run some basic machine learning tasks
(just testing). Now I'm trying to do a specific task and am unsure how to
proceed.
Imagine I have a data file containing the following columns: user_id, item_id,
and rating, where rating is how each user rated the item on a scale of -1 to 1
(the necessity of negative ratings will become apparent in a minute).
Ultimately, what I'm trying to do is create a similarity matrix that measures
the similarity between all pairs of USERS. To do this, I would like to
transform the users' ratings into a matrix (rows are users, columns are items)
and then run RowSimilarity to find the dot product / cosine between all rows.
I feel like my problem is simple and has probably been done 1000 times, but I
can't seem to find any documentation directly on the subject. The best I've
been able to do so far is use the similaritem function (where I've swapped item
for user). While it works and gives decent results, it's mathematically not
quite what I want. Help!
Thanks!
Jonathan
