Hidden Markov Models are used for modelling systems that are assumed to be Markov processes with hidden (i.e. unobserved) states.

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How can I train a HMM model for character recognition in preparation for subsequent word recognition?

I want to train a character HMM to recognize words, but I don't know how to train it. Do I train each character HMM first, or should I train the global HMM that attempts to recognize words by ...
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Strategy for estimating a more complex hidden markov model (HMM)

I have a HMM in mind where emission probabilities change over time (not dependent on state). For example, suppose I have two states and four possible emissions. If in state 1, emission probabilities ...
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General HMM training procedure?

I am new to EM algorithm, studying Hidden Markov Model. During training my HMM by EM, I am very confused on the data setting. (text processing) Please confirm whether my EM usage is okay or not. At ...
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HMM prior on stationary probability

I am trying to model a sensor that when mis-calibrated tends to vibrate alot (or atleast high varying readings). I used a HMM to model these vibrations. It is known that the sensor was calibrated ...
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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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Transition/emission probabilities POS tagger English

is there an freely available online version of transition and emission probabilities for an HMM model used for POS tagging English text? It seems like there are many powerful existing taggers out ...
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HMM toolbox matlab - joint distribution

I would like to use the HMM toolbox from matlab, but in the example of function hmmestimate they use only one variable distribution but I need to use joint distribution since I have multiple emission ...
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58 views

Finding a pattern in time series data

I have time series data. I am looking for a procedure to find if a particular pattern exists in the time series. To make it more clear, suppose I have a base time series in which the check for the ...
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Proof that Markov Property is not Satisfied at any Order?

My textbook has this figure in it: The textbook then says, Using d-separation, we can see there is always a path connecting $x_n$ and $x_{m}$ via the latent variables. This makes sense to me because ...
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Hidden Markov model - Time Granularity

Is Hidden Markov model sensitive on time granularity? I mean if I train HMM parameters on dataset which time granularity is 1 minute. May I use the transition matrix and emissions distributions for ...
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Hidden Markov Model with sequence of 1

I'm not experienced with HMM. I read some research papers about HMM and they mention 3 basic problems. One of them is to find the probability of a sequence of $k$ emitted symbols $(S = x_1, x_2,..., ...
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Estimating transition probability matrix for a given parameters

I am dealing with a hidden Markov model for variable $X_{t+1}$ where $X_{t+1}$ = $\alpha_{t}$$X_{t}$ + $(1-\alpha_{t})$$Z_{t}$ $X_{t}$ is an indication variable indicating whether an individual is ...
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Hidden Markov model and regime detection on historical data

I use depmixs4 package for stock market regime detection. Here is my code: ...
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HMM with variable length input

My task is to calculate the likelihood of a word belonging to to a certain group. My training set is comprised of words that are variable in length. If the length of words was equal , I would have ...
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Is this a correct explanation of the markov assumption?

Here is a description of a the markov assumption (taken from http://di.ubi.pt/~jpaulo/competence/tutorials/hmm-tutorial-1.pdf) : Given W = word is this also a valid explanation of the markov ...
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Time series pattern recognition tools

I have a matrix of 500 X 12 of time series, represented by each row. The columns being the 12 sampling times. I have also another matrix of 500 X 1 corresponding to 500 time series of which we only ...
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EM vs. direct numerical optimization of likelihood function in high-dimensional Markov-Switching / HMM

I am currently estimating a Markov-switching model with many parameters using direct optimization of the log likelihood function (through the forward-backward algorithm). I do the numerical ...
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sample size to train HMM

what the sample size is needed to train HMM? Is there a common method used to determine how many training samples are required to train a HMM , I am asking because I have a large dataset for training ...
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What is the optimal observation sequence length to train HMM?

I want to train HMM based on 11000 files each has a long sequence, this huge number to train, training time is too much, how I will choose the t = observation length to train HMM?
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27 views

How may I work out Name Entity Resolution?

I am trying to work out a Name Entity Recognition (NER) problem. I am presently trying to work around two supervised approaches of Maximum Entropy (MaxEnt) and (HMM). I like to extend the work to Name ...
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Kullback-Leibler and Battacharyya divergences between Hidden Markov Models with discrete emissions

Im trying to figure out how to compute KL or Battacharyya divergences between two HMMs models. I found papers which are about HMMs with normaly distributed emissions, but nothing for discrete ...
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20 views

HMM - derivative of the log-probability of the observations knowing the parameters

I'd like to use $P(O_{0..T}|\lambda)$ (probability of a sequence of observations knowing the hmm parameters) as a regularisation energy in an optimisation framework. The dimensionality of the ...
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How do I find the hidden states of a HMM for a non time series data? How does EM Algorithm play a role in HMM?

I am a beginner in machine learning. My project requires me to model user intentions using HMM i.e based on parameters like no.of clicks, time on page, etc I have to model whether the user wants to ...
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Hidden Markov Model for anomaly detection

In Hidden Markov Model, it is possible to compute probability of observation sequence by applying forward algorithm given learned model. We can detect anomaly sequences by this algorithm simply by ...
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How can I predict a post`s or a topic`s popularity and trend of reddit.com with hidden markov model(HMM)?

I have a project that I want to detect the hot topic or trending topic on the bbs. If I want to know whether the topic will become popular,trending or decline in the future? If I get some posts ...
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What types of HMM are there?

I can think of: Factorial Hierarchical Layered Nested 'standard' others?
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Learn a random walk process with RTS smoother

I'm trying to learn a random walk process as described at section 7 of http://www.cs.cmu.edu/~epxing/papers/SDM08_Ahmed.pdf I have a set of points over N epochs. Given a set of clusters $K$, every ...
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How may I create a large annotated Corpus for training?

I am trying to create an annotated corpus of few million words. I want to use it as training data for some supervised algorithm. I may try to implement a task like Parts of Speech(PoS) Tagging or Name ...
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Analysis of classification result

Assume you observed a system for 24 hours and collected data points each minute (each data points contain some host information like cpu_usage,... All elements are numeric). Also, there is a trained ...
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1answer
36 views

Forward-Backward Algorithm explanations

I am studying the Forward-Backward Algorithm from HMMs and the forward-backward algorithm by Ramesh Sridharan I don't understand how to get $(1,3,4)^{T}$ in the example below. Could someone help to ...
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How to test independence of two markov switching processes using likelihood ratio test

I would like to test for independence of two first order markov switching processes with two states each. I have read this can be done using the LR test (I know that this will be simulation based ...
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Offline Hidden Markov Model for time series analysis

One of the main principles of HMM is that the future state is dependent on previous state. This method is widely used for time series segmentation. However, for offline segmentation one can run HMM ...
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Supervised HMM Training in R

I'm looking for an R package that implements the supervised training of Hidden Markov Models. By supervised, I mean given a sequence of observations, we know which ...
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Build HMM of text data in R

I'm trying to make my own HMM tagging in R but don't know how to estimate parameter values since the packages I have been working with haven't worked with my data. The latest package I have been ...
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84 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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Correlated features in dataset

I undestand in general that it is important to take correlational structure into account while applying almost any statistical techniques. First question - could you help with the examples why it is ...
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Is the following a standard HMM variant?

I have a problem that looks to me like a HMM variant. Could somebody confirm that I am on the right track modelling this and possibly tell me the name of this HMM variant if it is a standard HMM ...
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Understanding a paper on a modified HMM

Link to the paper here. In section 3.3 the authors define their modified Hidden Markov Model, which I don't quite understand. My main question is when coding the Baum Welch algorithm for this HMM ...
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Music Genre Classification using combined SVM and HMM

We are doing a Music Genre Classification software using C#. We want to know if combining HMM and SVM as a classifier, by using the distance of trained data on the hyperplane as an input sequence for ...
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Continuous HMM library/Tool for continuous gesture recognition

There are many HMM tools, but most of them only support discrete density HMM (like Matlab). even the tools that support continuous density HMM can only be used for discontinuous gesture recognition. ...
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emission matrix in hidden markov model

I'm using a Hidden Markov Model for fraud prediction in credit card. I have already created the transition matrix using data from a set of training data data in term like this LLMHLHLMMLHH. I can't ...
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how to write down dynamical state space models with deterministic variables in PyMC?

is it possible to write down this simple dynamical system in pymc? $R_0 \sim Normal(\mu_r, \sigma_r)$ $Z_0 \sim Normal(\mu_z, \sigma_z)$ $R_t \sim Normal(R_{t-1}, \sigma_r)$ $Z_t = Z_{t-1} + ...
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How do you factor covariates into your hidden markov model?

I am currently implementing a Hidden Markov Model in Python and would like to add covariates to my model. There are 2 categorical covariates each covariate can take up to 4 values. For each ...
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HMM Model Selection

What is the process for selecting a model for an HMM? Say the data is time sequences, where each time sequence represents a class. I can used Baum-Welch to train, but I don't know how to determine ...
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Hidden Markov Model prior

Suppose I have a set of time sequences, and that each time sequence is representative of a class. I can train several HMMs using Baum-Welch, one HMM per class. Let all HMMs have the same number of ...
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Is it possible that maximal probabilities in hidden markov model are same for all sates?

I developed forward/backward algorithm for calculating probabilities for each state in hidden markov model and I got that maximal probabilities are the same in final probability matrix. This is data ...
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27 views

Classification using HMM

I would like to use HMM to classify a sequence of alphabets while preserving their orders. Just to put it formally, I am looking to compute $p(c|x_{1},x_{2}\ldots, x_{n})$ where ${x_{1},x_{2}\ldots, ...
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Hidden Markov Models and Viterbi Algorithm: Fair and Biased Die

So following is the problem that I am trying to solve using Viterbi algorithm and HMM: Before attempting to write a program, I want to do this problem by hand for the first 3 observations($651$). ...
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Hidden Markov Model and Viterbi algorithm: Understanding the Casino Problem?

I am deeply struggling with understanding how to apply the Viterbi algorithm. From my course notes, I have the following simple(I'm told) example: If the sequence ...
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How do I consider the whole training set in the process of Hidden Markov Model training?

I'm trying to train a Hidden Markov Model following theory from the book "Pattern Classification" by Duda, Hart, and Sotrk. For the HMM learning they discuss Forward-Backward algorithm there, ...