About the missing days of the week: I failed to record the days of the week for the other four ratings.
On Mon, Nov 22, 2010 at 11:24 PM, Lance Norskog <[email protected]> wrote: > The GroupLens dataset has User, Item, Rating and Timestamp. > We will use the rating of 1-5 as-is, but will reduce the timestamp > field to day of the week. > The lack of a rating defaults two 3 (neutral). There are 5 ratings > total in the sample: > > U1, I1, 2, ? > U1, I3, 4, ? > U2, I1, 4, ? > U2, I2, 5, T > U2, I3, 3, ? > > (We'll get to the question marks later.) > Now, make two matrices, User v.s. Item and Item v.s. Day of the Week. > User v.s. Item contains ratings, and Item v.s. Day of the Week > contains the number of rating records for that item on that day of the > week: ratings only cover Sunday, Monday and Tuesday. > > Formatting tables in kerned fonts just plain doesn't work, thus the > alternate format. > > 2 Users v.s. 3 Items: > I1,I2,I3 > { > U1 {2,3,4} > U2 {4,5,3} > } > > 3 Items v.s. 7 Days of the Week > S,M,T,W,T,F,S > { > I1 {1,0,1,0,0,0,0} > I2 {0,0,1,0,0,0,0} > I3 {0,1,1,0,0,0,0} > } > > Now, multiply these two matrices. The product is 2 Users v.s. 7 Days > of the Week: > S,M,T,W,T,F,S > { > U1 {2,4,9,0,0,0,0} > U2 {4,3,12,0,0,0,0} > } > > This matrix carries the total amount of enthusiasm for each user on > each day. To get the average enthusiasm of each user, divide each row > by the total number of ratings per day: > S,M,T,W,T,F,S > { > U1 {2,4,3,0,0,0,0} > U2 {4,3,4,0,0,0,0} > } > > Did I get this right, Ted? > > BTW, where are your slides for this topic? I've seen them a couple of > times in presentations (live and on Fora.tv), but can't find them. > > -- > Lance Norskog > [email protected] > -- Lance Norskog [email protected]
