Viterbi algorithm hmm solved decoding example

okay, let's dive into the viterbi algorithm, a powerful tool for decoding hidden markov models (hmms). this tutorial will provide a comprehensive explanation, a solved example, and python code to illustrate its workings.

**i. introduction to hidden markov models (hmms)**

before we jump into the viterbi algorithm, it's crucial to understand the underlying concept of hidden markov models.

* **what is an hmm?**

an hmm is a statistical model used to describe systems that evolve over time in a probabilistic manner. it consists of two key components:

* **hidden states:** these are the underlying states of the system that are *not* directly observable. think of them as the "true" states that influence what we see. for example, in weather forecasting, the hidden states might be "sunny," "cloudy," and "rainy." we don't directly observe these states; rather, we infer them.

* **observations:** these are the things we *can* observe directly. these observations are influenced by the hidden states. for instance, we might observe someone carrying an umbrella (observation). this observation gives us information about the likely hidden state (e.g., "rainy").

* **key probabilities:**

to define an hmm, we need the following probabilities:

* **initial probabilities (π):** the probability of starting in a specific hidden state at time t=0. for example, `π[sunny] = 0.6` means there's a 60% chance the system starts in the "sunny" state.

* **transition probabilities (a):** the probability of transitioning from one hidden state to another. `a[sunny][cloudy] = 0.3` means that if it's currently "sunny," there's a 30% chance it will be "cloudy" tomorrow. formally, `a[i][j] = p(state_t+1 = j | state_t = i)`.

* **emission probabilities (b):** the probability of observing a specific observation given a hidden state. `b[sunny][ice cream] = 0.8` means that if the hidden state is "sunny," there's an 80% chance we'll observe someone buying ice cream. form ...

#ViterbiAlgorithm #HMM #databaseerror
Viterbi algorithm
HMM
hidden Markov model
decoding example
sequence alignment
optimal path
state transition
emission probabilities
dynamic programming
likelihood maximization
trellis diagram
forward algorithm
backward algorithm
probabilistic model
machine learning