Part 1: Compute Forward Variable for Hidden Markov Models

Compute the forward variable alpha for the observation sequence O=(0,1,0,2,0,1,0) given the HMM (without renormalization).

Part 1A: Forward Variable for HMM with Two States

The HMM for Part 1A is specified below:

A = [[0.66, 0.34],
    [1, 0]]
B = [[0.5, 0.25, 0.25],
    [0.1, 0.1, 0.8]]
pi = [0.8, 0.2]

Result
0.40, ?.????, 0.030230, 0.00559, ?.??????, ?.??????, ?.??????
0.02, 0.0136, ?.??????, 0.00822, ?.??????, ?.??????, 0.000035
           

Part 1B: Forward Variable for HMM with Three States

The HMM for Part 1B is specified below:

A = [[0.8, 0.1, 0.1],
     [0.4, 0.2, 0.4],
     [0, 0.3, 0.7]]
B = [[0.66, 0.34, 0],
     [0, 0, 1],
     [0.5, 0.4, 0.1]]
pi = [0.6, 0, 0.4]
            
Result
0.396, 0.107712, ?.??????, ?.??????, 0.003919, 0.001066, ?.??????
0.000, ?.??????, ?.??????, ?.??????, ?.??????, ?.??????, ?.??????
0.200, 0.071840, 0.030530, ?.??????, 0.003916, ?.??????, 0.000492
          

Part 2: Compute Backward Variable for Hidden Markov Models

Compute the backward variable beta for the observation sequence O=(0,1,0,2,0,1,0) given the HMM (without renormalization).

Part 2A: Backward Variable for HMM with Two States

The HMM for Part 2A is identical to the HMM for Part 1A.

Result
?.??????, ?.??????, 0.015187, ?.??????, ?.??????, 0.364, 1.0
0.001314, ?.??????, ?.??????, 0.038530, ?.??????, ?.???, ?.?
           

Part 2B: Backward Variable for HMM with Three States

The HMM for Part 2B is identical to the HMM for Part 1B.

Result
?.??????, ?.??????, 0.006823, ?.??????, ?.??????, ?.???, ?.?
0.001862, ?.??????, ?.??????, ?.??????, ?.??????, 0.464, ?.?
0.002140, ?.??????, ?.??????, 0.034300, ?.??????, ?.???, ?.?
               

Part 3: Viterbi Algorithm

Find the most probable state sequence for the observation sequence O=(0,1,0,2,0,1,0) given the HMM using the Viterbi algorithm.

In this problem, both the indices of observation symbols and the state indices are assumed to be zero-based, i.e., the first row of A corresponds to state 0, second row of A corresponds to state 1 and so forth. This is also true for the indexing of the elements of pi. Similarly, the first column of B corresponds to observation symbol 0, the second column of B corresponds to observation symbol 1, and so on.

Part 3A: Viterbi Algorithm for HMM with Two States

The HMM for Part 3A is identical to the HMM for Part 1A.

Result
?, ?, ?, ?, ?, ?, ?
        

Part 3B: Viterbi Algorithm for HMM with Three States

The HMM for Part 3B is identical to the HMM for Part 1B.

Result
2, ?, ?, 1, ?, ?, ?
            

Part 4: Complete the First Project Proposal Peer Review

The peer review is submitted separately in Canvas.

Part 5: Complete the Second Project Proposal Peer Review

The peer review is submitted separately in Canvas.

Part 6: Complete the Third Project Proposal Peer Review

The peer review is submitted separately in Canvas.