Hidden Markov Models

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Probabilis1c   Graphical   Models  

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Hidden   Markov   Models   Daphne Koller

Hidden Markov Models S

S’

S0

O’

0.3

s1

s2

S2

S3

O1

O2

O3

0.1

0.5 0.7

S1

0.4 0.6

s3

0.5

s4

0.9 Daphne Koller

Numerous Applications •  •  •  • 

Robot localization Speech recognition Biological sequence analysis Text annotation

Daphne Koller

Robot Localization u

(0)

u

u

(1)

(t-1)

control signal robot pose

S(0)

S(1)

S(2)

o(1)

o(2)

...

S(t)

map sensor observation

o(t) Daphne Koller

Speech Recognition

Dan Jurafsky, Stanford

Daphne Koller

Segmentation of Acoustic Signal

Dan Jurafsky, Stanford

Daphne Koller

Phonetic Alphabet •  •  •  •  •  •  •  •  •  •  •  •  •  • 

AA AE AH AO AW AY B CH D DH EH ER EY F

odd at hut ought cow hide be cheese dee thee Ed hurt ate fee

AA D AE T HH AH T AO T K AW HH AY D B IY CH IY Z D IY DH IY EH D HH ER T EY T F IY

•  •  •  •  •  •  •  •  •  •  •  • 

• 

G HH IH IY JH K L M N NG OW OY

P

green he it eat gee key lee me knee ping oat toy

pee

http://www.speech.cs.cmu.edu/cgi-bin/cmudict

G R IY N HH IY IH T IYT JH IY K IY L IY M IY N IY P IH NG OW T T OY

P IY

•  •  •  •  •  •  •  •  •  •  •  • 

R S SH T TH UH UW V W Y Z ZH

read sea she tea theta hood two vee we yield zee seizure

R IY D S IY SH IY T IY TH EY T AH HH UH D T UW V IY W IY Y IY L D Z IY S IY ZH ER

Daphne Koller

Word HMM

Dan Jurafsky, Stanford

Daphne Koller

Phone HMM

Dan Jurafsky, Stanford

Daphne Koller

Recognition HMM

Dan Jurafsky, Stanford

Daphne Koller

Summary •  HMMs can be viewed as a subclass of DBNs •  HMMs seem unstructured at the level of random variables •  HMM structure typically manifests in sparsity and repeated elements within the transition matrix •  HMMs are used in a wide variety of applications for modeling sequences Daphne Koller