I am trying to implement the Slope One algorithm through PHP for a custom member recommendation. For this, I use the OpenSlopeOne library . The problem I am facing is that the recommendations created are not related to the user.
I currently have two tables: user_ratings and slope_one. The user_ratings table is pretty straight forward. It contains the rating of each item given by this user (user_id, item_id and user_item_rating). The slope_one table follows the default OpenSlopeOne schema: item_id1, item_id2, time, and rating.
The slope_one table is populated using the following SQL procedure:
CREATE PROCEDURE `slope_one`()
begin
DECLARE tmp_item_id int;
DECLARE done int default 0;
DECLARE mycursor CURSOR FOR select distinct item_id from user_ratings;
DECLARE CONTINUE HANDLER FOR NOT FOUND set done=1;
open mycursor;
while (!done) do
fetch mycursor into tmp_item_id;
if (!done) then
insert into slope_one (select a.item_id as item_id1,b.item_id as item_id2,count(*) as times, sum(a.rating-b.rating) as rating from user_ratings a, user_ratings b where a.item_id = tmp_item_id and b.item_id != a.item_id and a.user_id=b.user_id group by a.item_id,b.item_id);
end if;
END while;
close mycursor;
end
, :
SELECT
item.*
FROM
slope_one s,
user_ratings u,
item
WHERE
u.user_id = '{USER_ID}' AND
s.item_id1 = u.item_id AND
s.item_id2 != u.item_id AND
item.id = s.item_id2
GROUP BY
s.item_id2
ORDER BY
SUM(u.rating * s.times - s.rating) / SUM(s.times) DESC
LIMIT 20
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