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From: "Dinesh B Vadhia" <dineshbvadhia@hotmail.com>
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Subject: Re: Matrix-based recommendation analysis
Date: Thu, 25 Nov 2010 02:12:29 -0800
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Hello!  Have looked at the presentation and trying to get my head around =
it:

i.  is collaborative filtering being bypassed?
ii.  are new entries (observations) added dynamically or as a batch =
process?

=20


From: Ted Dunning=20
Sent: Tuesday, November 23, 2010 8:10 AM
To: user@mahout.apache.org=20
Subject: Re: Matrix-based recommendation analysis


For cross recommender comprehension, I recommend something like the =
example
in my slide show.  In that example, users issued query terms (giving the =
u x
q matrix B) and they watched videos (giving the u x v matrix A).  The =
cross
recommendation is a smoothed version of A' B (which result is v x q).

This matrix could be used to take query terms and recommend videos.  =
That is
(A' B) q =3D v.  With suitable cleanup of the A'B to suppress spurious
entries, this makes a workable search engine.

Bringing a concept like days of the week into the mix is a bit =
confusing.
 That could give you a smoothed popularity of content per day of the =
week,
but that is normally done by much simpler means.  The biggest difference =
is
that you can't pick three days of the week, but you can put three terms =
into
a query.

On Tue, Nov 23, 2010 at 12:15 AM, Lance Norskog <goksron@gmail.com> =
wrote:

> I'm not trying to distinguish them. That is the "find the Netflix =
user"
> paper :)
>
> I just want to understand the cross-recommender concept, that's all.
> Yes, this sample is too small to impute "enthusiasm"- the numbers are
> recommendation values.
>
> (If the rest of you want to follow along:
> http://www.slideshare.net/tdunning/intelligent-search , slides 35-36)
>
> On Mon, Nov 22, 2010 at 11:50 PM, Sean Owen <srowen@gmail.com> wrote:
> > (PS I don't think that link from Ted is publicly visible but try
> > http://www.slideshare.net/tdunning )
> >
> > Maybe I'm walking into half of a another conversation but what's the
> > question or goal here?
> >
> > I don't think the matrix product contains quite what you're saying.
> > For example U1 records only 2 ratings but has some "enthusiasm" on 3
> > separate days in the matrix product. The product is mashing together
> > item-day associations from all users and applying them to each user.
> >
> > Conceptually user-item-day is the 3-dimensional matrix that it =
sounds
> > like, if you want to distinguish associations from different users =
to
> > different items on different days.
> >
> >
> > On Tue, Nov 23, 2010 at 7:24 AM, Lance Norskog <goksron@gmail.com>
> 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
> >> lance.norskog@gmail.com
> >>
> >
>
>
>
> --
> Lance Norskog
> goksron@gmail.com
>

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