Statistical Learning
An Introduction to Support Vector Machines
The authors believe that SVMs are a topic now sufficiently mature that it should be viewed as its own subfield of machine learning. SVMs, first introduced by Vladimir Vapnik, are a type of linear learning machines much like the famous perceptron algorithm and, thus, function to classify input patterns by first being trained on labeled data sets (supervised learning). However, SVMs represent a significant enhancement in function over perceptrons. The power of SVMs lies in their use of nonlinear kernel functions that implicitly map input into high-dimensional feature spaces. In the high-dimensional feature spaces, linear classifications are possible; they become nonlinear in the transformation back to the original input space.
An Introduction to Support Vector Machines and Other Kernel-Based Learning Methods
A learning problem is referred to as classification if its output take discrete values in a set of possible categories and regression if it has continuous real-valued output. A simple and useful model of an input-output functional relationship is to assume that the output variable can be expressed approximately as a linear combination of its input vector components. These linear models include the linear least squares method for regression and the logistic regression method for classification. Because a linear model has limited prediction power by itself, there has been extensive research in nonlinear models such as neural networks. However, there are two major problems with the use of nonlinear models: First, they are theoretically difficult to analyze, and second, they are computationally difficult to solve.
18 striking AI Trends to watch in 2018 - Part 1 - Datahub
However, most of these researches and systems attain state-of-the-art performance only when trained with large amounts of data. With GDPR and other data regulatory frameworks coming into play, 2018 is expected to witness machine learning systems which can learn efficiently maintaining performance, but in less time and with less data. A data-efficient learning system allows learning in complex domains without requiring large quantities of data. For this, there would be developments in the field of semi-supervised learning techniques, where we can use generative models to better guide the training of discriminative models. More research would happen in the area of transfer learning (reuse generalize knowledge across domains), active learning, one-shot learning, Bayesian optimization as well as other non-parametric methods.
Which machine learning algorithm should I use?
This resource is designed primarily for beginner to intermediate data scientists or analysts who are interested in identifying and applying machine learning algorithms to address the problems of their interest. A typical question asked by a beginner, when facing a wide variety of machine learning algorithms, is "which algorithm should I use?" Even an experienced data scientist cannot tell which algorithm will perform the best before trying different algorithms. We are not advocating a one and done approach, but we do hope to provide some guidance on which algorithms to try first depending on some clear factors. The machine learning algorithm cheat sheet helps you to choose from a variety of machine learning algorithms to find the appropriate algorithm for your specific problems.
Crowdsourcing Meets Ecology: Hemispherewide Spatiotemporal Species Distribution Models
The processes that affect the distributions of animals and plants operate at multiple spatial and temporal scales, presenting a unique challenge for the development and coordination of effective conservation strategies, particularly for wide-ranging species. In order to study ecological systems across scales, data must be collected at fine resolutions across broad spatial and temporal extents. Crowdsourcing has emerged as an efficient way to gather these data by engaging large numbers of people to record observations. However, data gathered by crowdsourced projects are often biased due to the opportunistic approach of data collection. In this article, we propose a general class of models called AdaSTEM (for adaptive spatiotemporal exploratory models) that are designed to meet these challenges by adapting to multiple scales while exploiting variation in data density common with crowdsourced data.
Soft Actor-Critic: Off-Policy Maximum Entropy Deep Reinforcement Learning with a Stochastic Actor
Haarnoja, Tuomas, Zhou, Aurick, Abbeel, Pieter, Levine, Sergey
Model-free deep reinforcement learning (RL) algorithms have been demonstrated on a range of challenging decision making and control tasks. However, these methods typically suffer from two major challenges: very high sample complexity and brittle convergence properties, which necessitate meticulous hyperparameter tuning. Both of these challenges severely limit the applicability of such methods to complex, real-world domains. In this paper, we propose soft actor-critic, an off-policy actor-critic deep RL algorithm based on the maximum entropy reinforcement learning framework. In this framework, the actor aims to maximize expected reward while also maximizing entropy - that is, succeed at the task while acting as randomly as possible. Prior deep RL methods based on this framework have been formulated as Q-learning methods. By combining off-policy updates with a stable stochastic actor-critic formulation, our method achieves state-of-the-art performance on a range of continuous control benchmark tasks, outperforming prior on-policy and off-policy methods. Furthermore, we demonstrate that, in contrast to other off-policy algorithms, our approach is very stable, achieving very similar performance across different random seeds.
A Nonlinear Kernel Support Matrix Machine for Matrix Learning
In many problems of supervised tensor learning (STL), real world data such as face images or MRI scans are naturally represented as matrices, which are also called as second order tensors. Most existing classifiers based on tensor representation, such as support tensor machine (STM) need to solve iteratively which occupy much time and may suffer from local minima. In this paper, we present a kernel support matrix machine (KSMM) to perform supervised learning when data are represented as matrices. KSMM is a general framework for the construction of matrix-based hyperplane to exploit structural information. We analyze a unifying optimization problem for which we propose an asymptotically convergent algorithm. Theoretical analysis for the generalization bounds is derived based on Rademacher complexity with respect to a probability distribution. We demonstrate the merits of the proposed method by exhaustive experiments on both simulation study and a number of real-word datasets from a variety of application domains.
Higher-order clustering in networks
Yin, Hao, Benson, Austin R., Leskovec, Jure
A fundamental property of complex networks is the tendency for edges to cluster. The extent of the clustering is typically quantified by the clustering coefficient, which is the probability that a length-2 path is closed, i.e., induces a triangle in the network. However, higher-order cliques beyond triangles are crucial to understanding complex networks, and the clustering behavior with respect to such higher-order network structures is not well understood. Here we introduce higher-order clustering coefficients that measure the closure probability of higher-order network cliques and provide a more comprehensive view of how the edges of complex networks cluster. Our higher-order clustering coefficients are a natural generalization of the traditional clustering coefficient. We derive several properties about higher-order clustering coefficients and analyze them under common random graph models. Finally, we use higher-order clustering coefficients to gain new insights into the structure of real-world networks from several domains.
A Machine-Learning Approach to the Detection of Fetal Hypoxia during Labor and Delivery
In this article we focus on detecting hypoxia (or oxygen deprivation), a very serious condition that can arise from different pathologies and can lead to lifelong disability and death. We present a novel approach to hypoxia detection based on recordings of the uterine pressure and fetal heart rate, which are obtained using standard labor monitoring devices. The key idea is to learn models of the fetal response to signals from its environment. Then, we use the parameters of these models as attributes in a binary classification problem. A running count of pathological classifications over several time periods is taken to provide the current label for the fetus.
Installation Quickstart for Azure Machine Learning services
Azure Machine Learning services (preview) is an integrated, end-to-end data science and advanced analytics solution. It helps professional data scientists to prepare data, develop experiments, and deploy models at cloud scale. This Quickstart shows you how to create experimentation and model management accounts in Azure Machine Learning Preview. It also shows you how to install the Azure Machine Learning Workbench desktop application and CLI tools. Next, you take a quick tour of Azure Machine Learning Preview features by using the Iris flower dataset to build a model that predicts the type of iris based on some of its physical characteristics.