2. Otakus v.s. No. of Figures
A 5 3 0 1
B 4 3 0 1
C 1 1 0 5
D 1 0 4 4
E 0 1 5 4
There are some common factors behind otakus and characters.
http://www.quuxlabs.com/blog/2010/09/matrix-factorization-a-simple-tutorial-and-im
plementation-in-python/
3. Otakus v.s. No. of Figures
A
B
C
match
The factors are
latent.
Not directly
observable
No one cares
4. No. of Otakus = M No. of characters = N No. of latent factor = K
A 5 3 0 1
B 4 3 0 1
C 1 1 0 5
D 1 0 4 4
E 0 1 5 4
?1
?2
?3
? 4
? ?
? ?
??
? ?
? ?
Matrix X
r1
r2
rA
rB
Matrix X
?? 1 ?? 2
??1 ??2
? ?
? ?1
5
? ?
?? 1
4
??
?? 1
1
M
N
N
K
K
N
Singular value
decomposition
Minimize
Error
5. A 5 3 ? 1
B 4 3 ? 1
C 1 1 ? 5
D 1 ? 4 4
E ? 1 5 4
?1
?2
?3
? 4
? ?
? ?
??
? ?
? ?
?? 1
? ?
? ?1
5
? ?
?? 1
4
??
?? 1
1
?=
(?, ?)
(?
?
??
?
???? )
2
Find and by gradient descent
Minimizing
Only considering the
defined value
??
? ?
6. A 5 3 ? 1
B 4 3 ? 1
C 1 1 ? 5
D 1 ? 4 4
E ? 1 5 4
?1
?2
?3
? 4
? ?
? ?
??
? ?
? ?
A 0.2 2.1
B 0.2 1.8
C 1.3 0.7
D 1.9 0.2
E 2.2 0.0
Assume the dimensions of r are all 2 (there are two factors)
1 (
)
0.0 2.2
2 (
)
0.1 1.5
3 (
)
1.9 -0.3
-0.4
-0.3
2.2
0.6
0.1
7. More about Matrix Factorization
? Considering the induvial characteristics
? Ref: Matrix Factorization Techniques For
Recommender Systems
?=
(?, ?)
(?
?
??
?
+??+?? ????)
2
Find , , , by gradient descent
Minimizing
(can add regularization)
: otakus A likes to buy figures
: how popular character 1 is
? ?
? ?1
5 ? ?
? ?1
+? ? +?1 5
8. Matrix Factorization
for Topic analysis
? Latent semantic analysis (LSA)
? Probability latent semantic analysis (PLSA)
? Thomas Hofmann, Probabilistic Latent Semantic Indexing, SIGIR, 1999
? latent Dirichlet allocation (LDA)
? David M. Blei, Andrew Y. Ng, Michael I. Jordan, Latent Dirichlet Allocation,
Journal of Machine Learning Research, 2003
Doc 1 Doc 2 Doc 3 Doc 4
ͶY 5 3 0 1
Ʊ 4 0 0 1
y 1 1 0 5
xe 1 0 0 4
ί 0 1 5 4
Number in
Table:
Term frequency
(weighted by inverse
document frequency)
Latent factors are topics
( ؔ )
characterdocument,
otakusword
Editor's Notes
#2: ƽΨ
Figure
We can do dimension reduction on otakus and characters individually.