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 Learning Graphical Models


The best kept secret about linear and logistic regression

@machinelearnbot

All the regression theory developed by statisticians over the last 200 years (related to the general linear model) is useless. Regression can be performed as accurately without statistical models, including the computation of confidence intervals (for estimates, predicted values or regression parameters). The non-statistical approach is also more robust than theory described in all statistics textbooks and taught in all statistical courses. It does not require Map-Reduce when data is really big, nor any matrix inversion, maximum likelihood estimation, or mathematical optimization (Newton algorithm). It is indeed incredibly simple, robust, easy to interpret, and easy to code (no statistical libraries required).


The machine that wanted to be a mind ZDNet

AITopics Original Links

Artificial intelligence is one of humankind's greatest and oldest ambitions. The quest for non-human intelligence has captivated magicians, astrologers and mystics for as long as such professions have existed, but it took Aristotle to kick things off properly. He was the first to start organising laws of thought and the way they interact with the real world -- the basic concepts behind AI. That was in the third century BC, and 2,300 years later we still haven't cracked the problem. Part of the trouble is that nobody knows what AI is.


Book review: The Theory That Would Not Die ZDNet

AITopics Original Links

A few months ago, Autonomy founder and CEO Mike Lynch sold his company to HP for £7.1 billion. Back in 2000, when he had just become Britain's first software billionaire, Lynch gave an interview in which he talked about perception and explained how he built his company. It was based, he said, on the ideas of a little-known 18th-century clergyman called Thomas Bayes. That was my introduction to Thomas Bayes, whose ideas have been used to solve many intractable problems, a number of which Sharon Bertsch McGrayne studies in depth in The Theory That Would Not Die. In the last ten years, Bayes has become famous, and few working in the field of probability theory, computer intelligence or mathematics can have failed to have come into contact with his rule.


Learning Bayesian networks: The combination of knowledge and statistical data

AITopics Original Links

We describe a Bayesian approach for learning Bayesian networks from a combination of prior knowledge and statistical data. First and foremost, we develop a methodology for assessing informative priors needed for learning. Our approach is derived from a set of assumptions made previously as well as the assumption oflikelihood equivalence, which says that data should not help to discriminate network structures that represent the same assertions of conditional independence. We show that likelihood equivalence when combined with previously made assumptions implies that the user's priors for network parameters can be encoded in a single Bayesian network for the next case to be seen--aprior network--and a single measure of confidence for that network. Second, using these priors, we show how to compute the relative posterior probabilities of network structures given data.


Planning and acting in partially observable stochastic domains - ScienceDirect

AITopics Original Links

In this paper, we bring techniques from operations research to bear on the problem of choosing optimal actions in partially observable stochastic domains. We begin by introducing the theory of Markov decision processes (mdps) and partially observable MDPs (pomdps). We then outline a novel algorithm for solving pomdps off line and show how, in some cases, a finite-memory controller can be extracted from the solution to a POMDP. We conclude with a discussion of how our approach relates to previous work, the complexity of finding exact solutions to pomdps, and of some possibilities for finding approximate solutions.



Rare Disease Physician Targeting: A Factor Graph Approach

arXiv.org Machine Learning

In rare disease physician targeting, a major challenge is how to identify physicians who are treating diagnosed or underdiagnosed rare diseases patients. Rare diseases have extremely low incidence rate. For a specified rare disease, only a small number of patients are affected and a fractional of physicians are involved. The existing targeting methodologies, such as segmentation and profiling, are developed under mass market assumption. They are not suitable for rare disease market where the target classes are extremely imbalanced. The authors propose a graphical model approach to predict targets by jointly modeling physician and patient features from different data spaces and utilizing the extra relational information. Through an empirical example with medical claim and prescription data, the proposed approach demonstrates better accuracy in finding target physicians. The graph representation also provides visual interpretability of relationship among physicians and patients. The model can be extended to incorporate more complex dependency structures. This article contributes to the literature of exploring the benefit of utilizing relational dependencies among entities in healthcare industry.


Poisson--Gamma Dynamical Systems

arXiv.org Machine Learning

We introduce a new dynamical system for sequentially observed multivariate count data. This model is based on the gamma--Poisson construction---a natural choice for count data---and relies on a novel Bayesian nonparametric prior that ties and shrinks the model parameters, thus avoiding overfitting. We present an efficient MCMC inference algorithm that advances recent work on augmentation schemes for inference in negative binomial models. Finally, we demonstrate the model's inductive bias using a variety of real-world data sets, showing that it exhibits superior predictive performance over other models and infers highly interpretable latent structure.



Has voice control finally started speaking our language ?

AITopics Original Links

The problem with using the human voice to control computers is well known and well documented: it doesn't always work. You can find yourself adopting the aggressive tone of a belligerent tourist in a foreign land while digital assistants employ a range of apologetic responses ("I'm sorry, I didn't quite get that", "I'm sorry, I didn't understand the question"). We throw our arms up and complain about their shortcomings. Plenty of us have tried them, plenty of us have dismissed them as a waste of time. We tend not to hear about them doing the job perfectly well, because few people write impassioned tweets or blog posts about things that work flawlessly.