TTNT 12 May Hoc

8/2/2019 TTNT 12 May Hoc

1/31

Gii thiu HcGii thiu Hc mymyMM hnh Nave Ba eshnh Nave Ba es

T Hoi VitKhoa Cng ngh Thng tin

i hc Khoa hc T nhin [email protected]

1


2/31

Ni dungNi dung Gii thiu Hc my

Hc l g?

Cc vn v v d ca hc

M hnh Nave Bayes

2


3/31

Ti sao Hc My?Ti sao Hc My? Nhng tin b gn y trong thut ton v l thuyt

Dng l ang ln ca d liu trc tuyn Sc mnh tnh ton sn sng Ngnh cng nghip ang n r

Ba lnh vc thch hp cho hc my Khai thc d liu: s dng d liu c ci thin quyt

nh

Cc ng dng phn mm chng ta khng th lm bngtay Cc chng trnh t ti u ho

3


4/31

Hc l g?Hc l g? ghi nhiu g

hc cc s kin qua quan st v thm d ci thin cc k nng vn ng v/hay nhn

h vi l n

t chc tri thc mi thnh cc biu din tngqut, hiu qu

4


5/31

Cc loi hcCc loi hc Hc c gim st: cho trc mt tp mu cc

cp input/output, tm mt lut thc hin vic don cc kt xut gn vi cc input mi Gom cm: cho trc mt tp mu, nhng cha

,t nhin Hc tng cng: mt agent tng tc vi th

gii thc hin cc quan st, hnh ng, v cthng hay pht; n s hc chn cc hnhng theo cch nhn c nhiu phnthng

5


6/31

Hc mt HmHc mt HmCho trc mt tp mu cc cp input/output, tm mt hm

lm tt c cng vic biu din mi quan h Pht m: hm nh x t k t sang m thanh

Nm mt qu bng: hm nh x t v tr ch thnh qu

c cc ch vit tay: hm nh x t tp cc im nhthnh cc k t

Chn on bnh: hm nh x t cc kt qu xt nghim

thnh cc loi bnh tt

6


7/31

Cc vn hc mt hmCc vn hc mt hm ghi nh

ly trung bnh

tng qut ho

7


8/31

Bi ton v dBi ton v dKhi no th li xe (drive or walk) ? Ph thuc vo:

nhit (temperature) ma tuyt d kin (expected precipitation)

ngy trong tun (day of the week)

c y c cn i mua sm trn ng v hay khng(whether she needs to shop on the way home)

c y ang mc g (whats she wearing)

8


9/31

Ghi nhGhi nh

temp precip day shop clothes

80 none sat no casual walk

19 snow mon es casual drive

65 none tues no casual walk

19 snow mon yes casual

9


10/31

Ghi nhGhi nh

temp precip day shop clothes


19 snow mon es casual drive


19 snow mon yes casual drive

10


11/31

Ly trung bnhLy trung bnh

temp precip day shop clothes80 none sat no casual walk

80 none sat no casual drive

X l nhiu trong d liu

none sa no casua





80 none sat no casual

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12/31

Ly trung bnhLy trung bnh




none sa no casua






12


13/31

Nhiu cm binNhiu cm bin




none sa no casua





20 none sat no casual

13


14/31

Nhiu cm binNhiu cm bin




none sa no casua






14


15/31

Tng qut hoTng qut hotemp precip day shop clothes

71 none fri yes formal drive

38 none sun yes casual walk

62 rain weds no casual walk

X l d liu cha tng gp trc y

93 none mon no casual drive

55 none sat no formal drive




15


16/31

Tng qut hoTng qut hotemp precip day shop clothes

71 none fri yes formal drive

38 none sun yes casual walk

62 rain weds no casual walk

X l d liu cha tng gp trc y

93 none mon no casual drive

55 none sat no formal drive




58 rain mon no casual

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17/31

Mt v d khcMt v d khcf1 f2 f3 f4 y

0 1 0 1 1

0 1 0 1 11 1 0 1 1

0 1 0 1 1

f1 f2 f3 f4 y

0 1 0 1 1

0 0 0 1 10 1 0 1 1

0 0 0 1 1

= 1

= 0

1 1 0 1 0

1 1 0 1 0

1 1 0 1 0

0 1 0 1 01 1 0 1 0

= 1

= 0

0 0 0 1 0

0 0 0 1 0

0 0 0 1 0

0 1 0 1 00 1 0 1 0

17


18/31

Mt v d khc (tt)Mt v d khc (tt)f1 f2 f3 f4 y0 1 0 1 1

0 0 0 1 11 1 0 1 1

0 0 0 1 1

= ?

= ?

1 0 0 1 0

1 0 0 1 0

1 0 0 1 0

0 1 0 1 01 1 0 1 0

18


19/31

Nave BayesNave Bayes Da trn lut suy din xc sut ca Bayes

Cp nht xc sut ca gi thit (hm phn lp)da trn chng c

h n i hi x ln nh khi h

hp cc chng c

Thut ton c bit hu ch cho cc lnh vc cnhiu c trng

19


20/31

V dV d R1(1,1) = 1/5: t l tt c cc mu

dng (y=1) c c trng 1 = 1 R1(0,1) = 4/5: t l tt c cc mudng c c trng 1 = 0

f1 f2 f3 f4 y

0 1 1 0 10 0 1 1 1

1 0 1 0 1

0 0 0 0 1

1 0 0 1 0

1 1 0 1 0

1 0 0 0 01 1 0 1 0

1 0 1 1 0

20


21/31

V dV d R1(1,1) = 1/5: t l tt c cc mu

dng (y=1) c c trng 1 = 1 R1(0,1) = 4/5: t l tt c cc mudng c c trng 1 = 0

f1 f2 f3 f4 y

0 1 1 0 10 0 1 1 1

1 0 1 0 1

1 , =

m (y=0) c c trng 1 = 1

R1(0,0) = 0/5: t l tt c cc mum c c trng 1 = 0

0 0 0 0 1

1 0 0 1 0

1 1 0 1 0

1 0 0 0 01 1 0 1 0

1 0 1 1 0

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22/31

V dV dR1(1,1) = 1/5 R1(0,1) = 4/5

R1

(1,0) = 5/5 R1

(0,0) = 0/5

R2(1,1) = 1/5 R2(0,1) = 4/5

R2(1,0) = 2/5 R2(0,0) = 3/5

f1 f2 f3 f4 y

0 1 1 0 10 0 1 1 1

1 0 1 0 1

R3(1,1) = 4/5 R3(0,1) = 1/5

R3(1,0) = 1/5 R3(0,0) = 4/5

R4(1,1) = 2/5 R4(0,1) = 3/5R4(1,0) = 4/5 R4(0,0) = 1/5

0 0 0 0 1

1 0 0 1 0

1 1 0 1 0

1 0 0 0 01 1 0 1 0

1 0 1 1 0

22


23/31

DonDonR1(1,1) = 1/5 R1(0,1) = 4/5

R1(1,0) = 5/5 R1(0,0) = 0/5

R2(1,1) = 1/5 R2(0,1) = 4/5R2(1,0) = 2/5 R2(0,0) = 3/5

R3(1,1) = 4/5 R3(0,1) = 1/5

R3(1,0) = 1/5 R3(0,0) = 4/5

R4(1,1) = 2/5 R

4(0,1) = 3/5

R4(1,0) = 4/5 R4(0,0) = 1/5

Mu mi x = S(1) = R1(0,1) * R2(0,1) * R3(1,1) * R4(1,1) = .205

S(0) = R1(0,0) * R2(0,0) * R3(1,0) * R4(1,0) = 0

Ta c S(1) > S(0), do don lp 1

Trang 23


24/31

Thut ton HcThut ton Hc c lng t d liu, vi mi thuc tnh j, c min gi

tr Dj = {v1j, v2j,vnj}, tnh

ij

#( 1 1)( ,1)

# 1

i i

j

j i

x yR v

= ==

=D

yyP

i

#

)1(#)1(

===

ij

#( 1 0)( , 0)

#( 0)

i i

j

j i

x yR v

y

= ==

=

24

D

y

yP

i

#

)0(#

)0(

===


25/31

Thut ton DonThut ton Don Cho mt mu x mi, x = (x1, x2, xn), tnh

== )1,()1()1( ij xRyPS

Xut ra 1 nu S(1) > S(0)

25

== ,ij

xy


26/31

DonDonR1(1,1) = 1/5 R1(0,1) = 4/5

R1(1,0) = 5/5 R1(0,0) = 0/5

R2(1,1) = 1/5 R2(0,1) = 4/5R2(1,0) = 2/5 R2(0,0) = 3/5

R3(1,1) = 4/5 R3(0,1) = 1/5

R3(1,0) = 1/5 R3(0,0) = 4/5

R4(1,1) = 2/5 R

4(0,1) = 3/5

R4(1,0) = 4/5 R4(0,0) = 1/5

Mu mi x = S(1) = R1(0,1) * R2(0,1) * R3(1,1) * R4(1,1) = .205

S(0) = R1(0,0) * R2(0,0) * R3(1,0) * R4(1,0) = 0


Trang 26

lu c hai lp u c t

l bng nhau = 0.5


27/31

Thut ton DonThut ton Don Cho mt mu x mi, x = (x1, x2, xn), tnh

=

+==1

)1,(log)1(log)1(logj

ij xRyPS

Xut ra 1 nu logS(1) > logS(0)

Cng log s d dng hn nhiu so vi nhn cc s nh

27

=

+==1

,ogogogj ij

xy


28/31

Trnh s xut hin ca 1 hoc 0 trong xc sut

Php sa li LaplacePhp sa li Laplace

ij

#( 1 1) 1( ,1)

#( 1) 2

i i

j

j i

x yR v

y

= = +=

= +2#

1)1(#)1(

+

+===

D

yyP

i

ij

#( 1 0) 1( , 0)

#( 0) 2

i ij

j i

x yR v

y

= = +=

= +

28

2#

1)0(#)0(

+

+===

D

yyP

i

c 2 phn lp x c 2 gi tr


29/31

V d vi Sa liV d vi Sa liR1(1,1) = 2/7 R1(0,1) = 5/7

R1(1,0) = 6/7 R1(0,0) = 1/7

R2(1,1) = 2/7 R2(0,1) = 5/7

R2(1,0) = 3/7 R2(0,0) = 4/7

f1 f2 f3 f4 y

0 1 1 0 1

0 0 1 1 1

1 0 1 0 1

R3(1,1) = 5/7 R3(0,1) = 2/7

R3(1,0) = 2/7 R3(0,0) = 5/7

R4(1,1) = 3/7 R4(0,1) = 4/7R4(1,0) = 5/7 R4(0,0) = 2/7

0 0 0 0 1

1 0 0 1 0

1 1 0 1 0

1 0 0 0 01 1 0 1 0

1 0 1 1 0

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30/31

DonDonR1(1,1) = 2/7 R1(0,1) = 5/7

R1(1,0) = 6/7 R1(0,0) = 1/7

R2(1,1) = 2/7 R2(0,1) = 5/7R2(1,0) = 3/7 R2(0,0) = 4/7

R3(1,1) = 5/7 R3(0,1) = 2/7

R3(1,0) = 2/7 R3(0,0) = 5/7

R4

(1,1) = 3/7 R4

(0,1) = 4/7

R4(1,0) = 5/7 R4(0,0) = 2/7

Mu mi x = S(1) = R1(0,1) * R2(0,1) * R3(1,1) * R4(1,1) = .156

S(0) = R1(0,0) * R2(0,0) * R3(1,0) * R4(1,0) = .017


Trang 30


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iu cn nmiu cn nm Cc vn ca hc my

Hiu v s dng c m hnh Nave Bayes Nm c cc vn ca Nave Bayes

31

TTNT 12 May Hoc

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