ECENT technological achievements and globalization have increased data acquisition capability in almost all corners of human activities, ranging from scientific and engineering endeavors such as genomics, medical imaging, remote sensing, economics and finance, and all the way to people's personal lives with the emergence of social media through the world wide web and mobile networks. The enormous growth of data creates daunting challenges, not only in finding out how to store and access the data, but more importantly, how to process and make sense of it. Also, since data collection is expensive, we are somehow obliged to make good use of the data at hand, so it is obvious that for further progress, the development of efficient algorithms for processing big data is very important. Big data is usually considered in terms of the number of observations n and the number of variables p measured on each observation. In many branches of science such as genetics and medical imaging, the number of variables is very large and is often much larger than the number of observations. This scenario is often denoted as p n.

Of course, if you are an experienced Python programmer you will be able to skip this step. Even if so, I suggest keeping the very readable Python documentation handy. KDnuggets' own Zachary Lipton has pointed out that there is a lot of variation in what people consider a "data scientist." This actually is a reflection of the field of machine learning, since much of what data scientists do involves using machine learning algorithms to varying degrees. Is itnecessary to intimately understand kernel methods in order to efficiently create and gain insight from a support vector machine model?

The amount of data produced every day grows tremendously in most real-life domains, including medical imaging, genomics, text categorisation, computational biology, and many others. Although it appears beneficial at the first glance (more data could mean more possibilities of extracting and revealing useful underlying knowledge), handling massively large datasets became a challenging issue and attracts research attention, especially in the era of big data. This big data revolution affected many research fields, including statistics, machine learning, parallel computing, and computer systems in general [1]. Storing and analysing the acquired historical information should allow predicting the label of an incoming (unseen) feature vector, containing some quantified features of a given data example. If the labels are categorical, then we are to tackle the classification task (it's regression otherwise).

In this post I will explain the Support Vector Machines method. First, what is a Support Vector? It's the margins of an Hyperplane (linear or not) that divides two or more groups, whose margin (distance between two groups) must be maximized: The Hyperplane borders are H1 and H2 and the distance to be maximized is d1 and d2. First, let's do a regular Linear Regression with black dots (X1) and white dots (X2). You can easily see that the estimated Y (red line) barely touches some of the blue dots (real Y).

This paper investigates the supervised learning problem with observations drawn from certain general stationary stochastic processes. Here by \emph{general}, we mean that many stationary stochastic processes can be included. We show that when the stochastic processes satisfy a generalized Bernstein-type inequality, a unified treatment on analyzing the learning schemes with various mixing processes can be conducted and a sharp oracle inequality for generic regularized empirical risk minimization schemes can be established. The obtained oracle inequality is then applied to derive convergence rates for several learning schemes such as empirical risk minimization (ERM), least squares support vector machines (LS-SVMs) using given generic kernels, and SVMs using Gaussian kernels for both least squares and quantile regression. It turns out that for i.i.d.~processes, our learning rates for ERM recover the optimal rates. On the other hand, for non-i.i.d.~processes including geometrically $\alpha$-mixing Markov processes, geometrically $\alpha$-mixing processes with restricted decay, $\phi$-mixing processes, and (time-reversed) geometrically $\mathcal{C}$-mixing processes, our learning rates for SVMs with Gaussian kernels match, up to some arbitrarily small extra term in the exponent, the optimal rates. For the remaining cases, our rates are at least close to the optimal rates. As a by-product, the assumed generalized Bernstein-type inequality also provides an interpretation of the so-called "effective number of observations" for various mixing processes.

What are the limits of automated Twitter sentiment classification? We analyze a large set of manually labeled tweets in different languages, use them as training data, and construct automated classification models. It turns out that the quality of classification models depends much more on the quality and size of training data than on the type of the model trained. Experimental results indicate that there is no statistically significant difference between the performance of the top classification models. We quantify the quality of training data by applying various annotator agreement measures, and identify the weakest points of different datasets. We show that the model performance approaches the inter-annotator agreement when the size of the training set is sufficiently large. However, it is crucial to regularly monitor the self- and inter-annotator agreements since this improves the training datasets and consequently the model performance. Finally, we show that there is strong evidence that humans perceive the sentiment classes (negative, neutral, and positive) as ordered.

The stage and grade of psoriasis severity is clinically relevant and important for dermatologists as it aids them lead to a reliable and an accurate decision making process for better therapy. This paper proposes a novel psoriasis risk assessment system (pRAS) for stratification of psoriasis severity from colored psoriasis skin images having Asian Indian ethnicity. Machine learning paradigm is adapted for risk stratification of psoriasis disease grades utilizing offline training and online testing images. It uses two kinds of classifiers (support vector machines (SVM) and decision tree (DT)) during training and testing phases and two kinds of feature selection criteria (Principal Component Analysis (PCA) and Fisher Discriminant Ratio (FDR)), thus, leading to an exhaustive comparison between these four systems. Our database consisted of 848 psoriasis images with five severity grades: healthy, mild, moderate, severe and very severe, consisting of 383, 47, 245, 145, and 28 images respectively.

Classification schemes keep evolving & improving with recent publications. Those recent techniques involve multi-output classifications, ie, the response variable/s is 2 or more in comparison to standard classification of just a single variable say Y. The multi-class MIMO SVR (multi input multi output - support vector regression) is one of those new techniques, eg: the multi output could be 3 variables (as Gender, Age-bracket, Earning-bracket) & may be denoted as [G, A, E], where gender is 2 class (male, female), age-bracket is multiclass (student, young-adult, adult, retired) & age-bracket is also multiclass. MIMO SVR can predict the 3 output variables class labels at once. The other multiclass MIMO schemes includes CANFIS (Co-Active Neuro-Fuzzy Inference System) & its variants.

Support vector machines is one of the most popular methods of classification in machine learning although they can be used as a black box, understanding what's happening behind scenes can be very useful not to mention interesting. In an internal learning course, I decided to implement SVMs and my objective with this article to mention some of the difficulties encountered. If you're planning to explore on how to implement support vector machines, have in mind this issues and the problem will be a little bit more easy to affront.

Classification Ensemble, which uses the weighed polling of outputs, is the art of combining a set of basic classifiers for generating high-performance, robust and more stable results. This study aims to improve the results of identifying the Persian handwritten letters using Error Correcting Output Coding (ECOC) ensemble method. Furthermore, the feature selection is used to reduce the costs of errors in our proposed method. ECOC is a method for decomposing a multi-way classification problem into many binary classification tasks; and then combining the results of the subtasks into a hypothesized solution to the original problem. Firstly, the image features are extracted by Principal Components Analysis (PCA). After that, ECOC is used for identification the Persian handwritten letters which it uses Support Vector Machine (SVM) as the base classifier. The empirical results of applying this ensemble method using 10 real-world data sets of Persian handwritten letters indicate that this method has better results in identifying the Persian handwritten letters than other ensemble methods and also single classifications. Moreover, by testing a number of different features, this paper found that we can reduce the additional cost in feature selection stage by using this method.