Learning Graphical Models


Artificial Intelligence #3:kNN & Bayes Classification method

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This can be thought of as the training set for the algorithm, though no explicit training step is required.by Sobhan N. What you'll learn Use k Nearest Neighbor classification method to classify datasets. Write your own code to make k Nearest Neighbor classification method by yourself. Use k Nearest Neighbor classification method to classify IRIS dataset. Use Naive Bayes classification method to classify datasets.


What Skills are AI Firms Expecting From its Employees? - SignitySolutions

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Artificial Intelligence (AI) also known as machine learning has come a long way in the recent few years. Instead of being a subject of discussion, it has become a reality. There has been ready integration of AI across a large number of industries. This has given rise to several AI development companies across the world. These AI consulting firms offer services to their clients and help with the integration of AI in their operations.


MIT CSAIL's CommPlan AI helps robots efficiently collaborate with humans

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In a new study, researchers at MIT's Computer Science and Artificial Intelligence Lab propose a framework called CommPlan, which gives robots that work alongside humans principles for "good etiquette" and leave it to the robots to make decisions that let them finish tasks efficiently. They claim it's a superior approach to handcrafted rules, because it enables the robots to perform cost-benefit analyses on their decisions rather than follow task- and context-specific policies. CommPlan weighs a combination of factors, including whether a person is busy or likely to respond given past behavior, leveraging a dedicated module -- the Agent Markov Model -- to represent that person's sequential decision-making behaviors. It consists of a model specification process and an execution-time partially observable Markov decision process (POMDP) planner, derived as the robot's decision-making model, which CommPlan uses in tandem to arrive at the robot's actions and communications policies. Using CommPlan, developers first specify five modules -- a task model, communication capability, a communication cost model, a human response model, and a human action-selectable model -- with data, domain expertise, and learning algorithms.


Hidden Markov Model -- Implemented from scratch

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The Internet is full of good articles that explain the theory behind the Hidden Markov Model (HMM) well (e.g. 1, 2, 3 and 4). However, many of these works contain a fair amount of rather advanced mathematical equations. While equations are necessary if one wants to explain the theory, we decided to take it to the next level and create a gentle step by step practical implementation to complement the good work of others. In this short series of two articles, we will focus on translating all of the complicated mathematics into code. Our starting point is the document written by Mark Stamp.


What is Bayes Theorem?

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If you've been learning about data science or machine learning, there's a good chance you've heard the term "Bayes Theorem" before, or a "Bayes classifier". These concepts can be somewhat confusing, especially if you aren't used to thinking of probability from a traditional, frequentist statistics perspective. This article will attempt to explain the principles behind Bayes Theorem and how it's used in machine learning. Bayes Theorem is a method of calculating conditional probability. The traditional method of calculating conditional probability (the probability that one event occurs given the occurrence of a different event) is to use the conditional probability formula, calculating the joint probability of event one and event two occurring at the same time, and then dividing it by the probability of event two occurring.


Glioma stages prediction based on machine learning algorithm combined with protein-protein interaction networks

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In this study recently published in Genomics, the author team aimed to characterize molecular mechanisms associated with glioma progression stages by using machine learning and protein-protein interaction networks analysis. Background: Glioma is the most lethal nervous system cancer. Recent studies have made great efforts to study the occurrence and development of glioma, but the molecular mechanisms are still unclear. This study was designed to reveal the molecular mechanisms of glioma based on protein-protein interaction network combined with machine learning methods. Key differentially expressed genes (DEGs) were screened and selected by using the protein-protein interaction (PPI) networks.


In a Boltzmann machine, why isn't there a simple expression for the optimal edge weights in terms of correlations between variables?

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If we do this by using gradient ascent on the log-likelihood function, each step of gradient ascent involves an expensive expectation estimate using MCMC (or some cheaper approximation). Conceptually the edge weights represent the "interaction strength" between variables, i.e. $w_{ij}$ represents how much $x_i$ and $x_j$ "want" to be equal. It would make sense that variables that are highly positively correlated have large positive edge weights, and variables that are negatively correlated have negative edge weights. But this would imply that learning the edge weights is easy, because we could just calculate the correlations, apply some mapping and get the edge weights. Obviously that is not true or we wouldn't need the expensive algorithm.



Gradient-based Adaptive Markov Chain Monte Carlo

Neural Information Processing Systems

We introduce a gradient-based learning method to automatically adapt Markov chain Monte Carlo (MCMC) proposal distributions to intractable targets. We define a maximum entropy regularised objective function, referred to as generalised speed measure, which can be robustly optimised over the parameters of the proposal distribution by applying stochastic gradient optimisation. An advantage of our method compared to traditional adaptive MCMC methods is that the adaptation occurs even when candidate state values are rejected. This is a highly desirable property of any adaptation strategy because the adaptation starts in early iterations even if the initial proposal distribution is far from optimum. We apply the framework for learning multivariate random walk Metropolis and Metropolis-adjusted Langevin proposals with full covariance matrices, and provide empirical evidence that our method can outperform other MCMC algorithms, including Hamiltonian Monte Carlo schemes.


The Infinite Gamma-Poisson Feature Model

Neural Information Processing Systems

We address the problem of factorial learning which associates a set of latent causes or features with the observed data. Factorial models usually assume that each feature has a single occurrence in a given data point. However, there are data such as images where latent features have multiple occurrences, e.g. a visual object class can have multiple instances shown in the same image. To deal with such cases, we present a probability model over non-negative integer valued matrices with possibly unbounded number of columns. This model can play the role of the prior in an nonparametric Bayesian learning scenario where both the latent features and the number of their occurrences are unknown.