HIDDEN MARKOV MODEL Application of the conditional probability.
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HIDDEN MARKOV MODELApplication of the conditional probability
Markov Chains
Weather forecast problemFrom history, P(weathertomorrow|weathertoday):
Given today as sunny (S) what is the probability that the next following five days are S , C , C , R and S, having the above model?
Tomorrow
Today
Weather Sunny Cloudy Rainy
Sunny 0.7 0.2 0.1
Cloudy 0.05 0.8 0.15
Rainy 0.15 0.25 0.6
Markov Chains
We are looking for is the weather conditional probability P(Tomorrow/Today).
Assumption: tomorrow’s weather depends only on today’s condition => first order Markov chain.
P(q1=S,q2=S ,q3= C ,q4= C ,q5= R ,q6=S)= P(S)*P(S|S)*P(C|S)
*P(C|C)*P(R|C)*P(S|R)
=1*0.7*0.2*0.8*0.15*0.15
=0.0052
Hidden Markov Model
We don’t know exactly what is the next state.
aij=P(j|i)
S1 S2 S5S4S3
1,2,3
Hidden Markov Model
Start at S1, end at S5. Pick balls 6 times. What is the sequence of ball’s color?
Pick 1: S1
Sequence={ } R
2Go to S2….Repeat until finishing 4 ballsFor picking up the 5th ball, do the same exceptfinding next state because we need to finish at S5.
,R,G,Y,G,R
Random next state (aij)
Application of HMM
Speech recognition
Application of HMM
Silent
Consonant
A-Z
Vowel
A,E,I,O,U
Final
A-ZSilent
S1 S2 S3 S4 S5
a21
a11a22
a32 a43 a54
a33 a44