Iowa State Universitycs573x/Notes/cs573week3... · 2010-02-07 · 2 ! # Department of Computer...

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Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

2

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

11, 01,10, 00

11 10

01 00

1 0

c=A c=B

1 0

11 01

11 01

1 0

c=A c=B

10 00

10 00

c=A c=B

x 1 0 x

Tree 1 Tree 2 Data set

x

11, 01, 10, 00

y

Exa

mples

Class

3

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

C

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

4

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

5

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

6

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

7

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

8

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

9

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

P.

P , H

P ( )

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

10

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

11

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

P(X = H; Y = H) = 0.2. P(X= H; Y = T) = 0.4P(X = T; Y = H) = 0.3. P(X = T; Y = T) = 0.1H(X,Y)=-0.2log20.2+… 1.85P(X = H) = 0.6. H(X) 0.97P(Y = H) = 0.5. H(Y) = 1.0P(Y= H| X = H) = 0.2/0.6 = 0.333P(Y = T|X = H) = 1-0.333=0.667P(Y= H| X = T)= 0.3/0.4=0.75P(Y= T| X = T)=0.1/0.4=0.25 H(Y|X) 0.88

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Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

I(X,Y)=0?

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

13

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

S1

S2

SmS

Si Ci

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

14

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

I1 (t, d, l) +I2 (s, d, l) +I3 (t, b, l) -I4 (t, r, l) -I5 (s, b, l) -I6 (t, b, w) +I7 (t, d, w) +I8 (s, b, w) +

Height (tall, short)Hair (dark, blonde, red) Eye (blue, brown)

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

I1…I8

Height

I1 I3 I4 I6 I7 I2 I5 I8

t s

St Ss

Hair Hair

15

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

Hair

rd

+ -Eye

b

wl

+

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

P (h) h

P (D) D

P (h | D) h D

P (D | h) D h

16

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

17

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

hMAP = argmaxh

iHP(D | hi )P(hi )

= argmaxh

iH

log2 P Dhi( ) + log2 P hi( )( )

= argminh

iH

log2 P Dhi( ) log2 P hi( )( )

log2 P hi( ) = description length of hi under optimal encoding

of hypotheses

-log2P(D | hi ) = description length of data D given hi under optimal encoding based on P(D | hi )

MAP hypothesis learning implies Occam's razor!

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

X,

D = {ei =(Xi , di)|Xi X di=c(Xi )}

D

VH,D

D

18

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

i.i.d. samples imply

P D | h( ) = P ei | h( )i

= P Xi,di h( )i

= P di h,Xi( )i

P Xi | h( )

Assuming Xi are independent of h,

P D | h( ) = P(dii

| h,Xi )P Xi( )

P(di | h,Xi ) =1 if h(Xi ) = di;

P(di | h,Xi ) = 0 otherwise

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Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

P D( ) = P(D | hh H

)P(h) =1H

h VH, D

P Xi( )i

+ 0

h VH, D

=VH ,D

HP Xi( )

i

h VH ,D, we have

P(h |D) =P Dh( )P h( )

P D( )=

P Xi( )i

H

H

VH ,D P Xi( )i

=

1VH ,D

and h VH ,D, we have P(h |D) = 0

H D

20

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

H

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

21

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

D

hi

h h

hi

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

H

22

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

H

H

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

23

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

24

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

25

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

26

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

27

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

28

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

29

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

30

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

31

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

EntropyRatio(S | A)Entropy(S | A)

SplitEntropy(S | A)

SplitEntropy(S | A)| Si || S |i=1

Values(A )log2

| Si || S |

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

Entropy Impurity(Z) =ZiZi=1

Classeslog2

ZiZ

Gini Impurity(Z) =ZiZ

i j

Z j

Z

=1

ZiZ

2

i=1

Classes

32

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

Impurity(S | A) = Min

i Values(A )Impurity Si( ){ }

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

w

ASGain

ACost 1

12

+

-

ACost

ASGain2

33

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

Impurity(S) = ijij

SiS

S jS

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

34

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

35

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

36

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

37

Department of Computer Science

Artificial Intelligence Research Laboratory

Copyright Vasant Honavar, 2010

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