Questions tagged [viterbi-algorithm]

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Energy based learning for HMMs: Viterbi training

I understand why we want to maximise the posterior probability to find the most likely sequence of hidden variables but I've read that this is equivalent to minimising some concept of free energy. I'...
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1answer
89 views

Viterbi algorithm for finding most probable path with varying transition probabilities

I'm struggling to apply the Viterbi algorithm to a simple case of inferring hidden states where the transmission probabilities change. I've draw a picture below of the trellis with transition ...
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44 views

Is negative Viterbi Loss possible?

So I'm training a sequence-labeling model with a BiLSTM-CRF architecture, and I am getting negative values on Viterbi Loss. Is this possible? I'm using the following formula in my code, as specified ...
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17 views

Biased viterbi training result

I try to use GMM-HMM model to infer the topic of sentences in a short paragraph. While instead of using normal Baum-Welch optimization, I use viterbi training as follows. I use average of word ...
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66 views

Normalizing output of Viterbi algorithm

Viterbi algorithm can be used to solve problems in belief networks of the following kind: $$argmax_{x_{1:t}}P(x_{1:t}| e_{1:t})$$ where $e_{1:t} \in E^t$ are evidence variables and $x_{1:t} \in S^t$ ...
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1answer
321 views

Viterbi and forward-backward algorithm in HMM

I am learning HMM recently and got confused with the training problem (training model parameters and hidden state given outcome sequence). As far as I know, both Viterbi learning and Baum-Welch (...
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136 views

Classification Using The Hidden Markov Model

I am having difficulty understanding certain concepts regarding the classification using HMM. There are numerous post here and in the internet about that, but they never get to detail or they all ...
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1answer
53 views

Can all or most combinatoric optimization problems in Machine Learning be solved using Viterbi algorithm? [closed]

I am just scratching the surface of the topic but are there practical limitations even for Viterbi Algorithm? Also, are Viterbi Algorithm and dynamic programming equivalent?
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136 views

What if transitions and emissions in a hidden Markov model are not independent?

A Hidden Markov Model is given by transition and emission matrices. The transition matrix determine probability of "next states" as a function of the current state. The emission matrix determine the ...
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1answer
53 views

Produce Multiple Sequence Alignments using Profile HMMs

I have a few multiple sequence alignments and a few groups (let's say N) of unaligned sequences. I would like to learn the emission and transition probabilities from the multiple sequence alignments, ...
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1answer
510 views

Decode the most likely sequence of states for the following sequence

A two-state HMM is constructed from the measurements shown below. The mean length indicates the average time that the HMM stays in the state. Decode the most likely sequence of states (P/Y) for ...
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1answer
2k views

Matlab hmm viterbi algorithm calculated state sequence Probability

I have used matlab hmmviterbi function in my code for calculating the most probable state sequence from observation sequence. Is there any way to derive the probability (score) of this calculated ...
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1answer
626 views

Other method to find the most likely hidden state in HMM?

If I use Baum-Welch algorithm to best estimate the parameters for hidden Markov model, then I was thinking, instead of using Viterbi algorithm, why can't I just find the most likely hidden state for ...
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885 views

HMM for sequence classification in R

I have a dataset which includes sequence of DNA nucleotides (A,C,G,T) and each sequence has a gene index that is binary. i.e I'm trying to classify unknown sequence by using a hidden markov model in ...
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2answers
7k views

Calculating Emission Probability values for Hidden Markov Model (HMM)

I'm new to HMM and still learning. I'm currently using HMM to tag part-of-speech. To implement the viterbi algorithm I need transition probabilities ($ a_{i,j} \newcommand{\Count}{\text{Count}}$) and ...
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0answers
29 views

How large a training set do I need for an English POS tagger?

I'm trying to implement a POS tagger for English using the Viterbi algorithm on an HMM model. Right now, my results are poor and I'm not sure whether it's due to a bug or due to lack of training data. ...
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1answer
426 views

In what way does clustering help in classification?

I understand that with a K-means or DTW algorithm one can cluster time series using a distance criterion, i also understand that with a K-NN algorithm for example one can do pattern recognition and ...
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1answer
7k views

Explain Backward algorithm for Hidden Markov Model

I have implemented Viterbi and Forward algorithm, alas strangely I can't understand how does Backward algorithm work. Intuitively I feel like I need to do the same thing as in Forward only backwards, ...
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224 views

Using Viterbi Algorithm to find the most probable sequence

I have this problem, but I couldn't find any related literature. Let's assume that I have this arrival process (the system can fit just one user): With probability $P_a$ the next user is from class ...
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153 views

Predicting Trend using Hidden Markov Model

I am trying to predict exchange rates trend using Hidden Markov model (Viterbi Algorithm). For 2 state trending, I use A = [0.9 0.1; 0.1 0.9] as transition matrix and B = [1/N 1/N ....1/N; 1/N 1/N .....
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178 views

What is the difference between coupled HMM's viterbi algorithm and tranditional HMM's viterbi algorithm?

Can anyone show me what is the difference between coupled HMM's viterbi algorithm and tranditional HMM's viterbi algorithm? Is there any examples?
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5answers
41k views

What is the difference between the forward-backward and Viterbi algorithms?

I want to know what the differences between the forward-backward algorithm and the Viterbi algorithm for inference in hidden Markov models (HMM) are.
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2answers
21k views

What are the differences between the Baum-Welch algorithm and Viterbi training?

I am currently using Viterbi training for an image segmentation problem. I wanted to know what the advantages/disadvantages are of using the Baum-Welch algorithm instead of Viterbi training.