Support Vector Machines
Parallel Support Vector Machines: The Cascade SVM
We describe an algorithm for support vector machines (SVM) that can be parallelized efficiently and scales to very large problems with hundreds of thousands of training vectors. Instead of analyzing the whole training set in one optimization step, the data are split into subsets and optimized separately with multiple SVMs. The partial results are combined and filtered again in a'Cascade' of SVMs, until the global optimum is reached. The Cascade SVM can be spread over multiple processors with minimal communication overhead and requires far less memory, since the kernel matrices are much smaller than for a regular SVM. Convergence to the global optimum is guaranteed with multiple passes through the Cascade, but already a single pass provides good generalization.
Class-size Independent Generalization Analsysis of Some Discriminative Multi-Category Classification
We consider the problem of deriving class-size independent generaliza- tion bounds for some regularized discriminative multi-category classi- fication methods. In particular, we obtain an expected generalization bound for a standard formulation of multi-category support vector ma- chines. Based on the theoretical result, we argue that the formula- tion over-penalizes misclassification error, which in theory may lead to poor generalization performance. A remedy, based on a generalization of multi-category logistic regression (conditional maximum entropy), is then proposed, and its theoretical properties are examined.
An Auditory Paradigm for Brain-Computer Interfaces
Motivated by the particular problems involved in communicating with "locked-in" paralysed patients, we aim to develop a brain- computer interface that uses auditory stimuli. We describe a paradigm that allows a user to make a binary decision by focusing attention on one of two concurrent auditory stimulus sequences. Using Support Vector Machine classification and Recursive Chan- nel Elimination on the independent components of averaged event- related potentials, we show that an untrained user's EEG data can be classified with an encouragingly high level of accuracy. This suggests that it is possible for users to modulate EEG signals in a single trial by the conscious direction of attention, well enough to be useful in BCI.
Sub-Microwatt Analog VLSI Support Vector Machine for Pattern Classification and Sequence Estimation
An analog system-on-chip for kernel-based pattern classification and se- quence estimation is presented. State transition probabilities conditioned on input data are generated by an integrated support vector machine. Dot product based kernels and support vector coefficients are implemented in analog programmable floating gate translinear circuits, and probabil- ities are propagated and normalized using sub-threshold current-mode circuits. A 14-input, 24-state, and 720-support vector forward decod- ing kernel machine is integrated on a 3mm3mm chip in 0.5m CMOS technology. Experiments with the processor trained for speaker verifica- tion and phoneme sequence estimation demonstrate real-time recognition accuracy at par with floating-point software, at sub-microwatt power.
Density Level Detection is Classification
We show that anomaly detection can be interpreted as a binary classifi- cation problem. Using this interpretation we propose a support vector machine (SVM) for anomaly detection. We then present some theoret- ical results which include consistency and learning rates. Finally, we experimentally compare our SVM with the standard one-class SVM.
Following Curved Regularized Optimization Solution Paths
Regularization plays a central role in the analysis of modern data, where non-regularized fitting is likely to lead to over-fitted models, useless for both prediction and interpretation. We consider the design of incremen- tal algorithms which follow paths of regularized solutions, as the regu- larization varies. These approaches often result in methods which are both efficient and highly flexible. We suggest a general path-following algorithm based on second-order approximations, prove that under mild conditions it remains "very close" to the path of optimal solutions and illustrate it with examples. Many commonly used supervised learning methods can be cast in this form, including regularized 1-norm and 2-norm support vector machines [13, 4], regularized linear and logistic regression (i.e.
Support Vector Classification with Input Data Uncertainty
This paper investigates a new learning model in which the input data is corrupted with noise. We present a general statistical framework to tackle this problem. Based on the statistical reasoning, we propose a novel formulation of support vector classification, which allows uncer- tainty in input data. We derive an intuitive geometric interpretation of the proposed formulation, and develop algorithms to efficiently solve it. Empirical results are included to show that the newly formed method is superior to the standard SVM for problems with noisy input.
A Topographic Support Vector Machine: Classification Using Local Label Configurations
The standard approach to the classification of objects is to consider the examples as independent and identically distributed (iid). In many real world settings, however, this assumption is not valid, because a topo- graphical relationship exists between the objects. In this contribution we consider the special case of image segmentation, where the objects are pixels and where the underlying topography is a 2D regular rectangular grid. We introduce a classification method which not only uses measured vectorial feature information but also the label configuration within a to- pographic neighborhood. Due to the resulting dependence between the labels of neighboring pixels, a collective classification of a set of pixels becomes necessary.
Maximal Margin Labeling for Multi-Topic Text Categorization
In this paper, we address the problem of statistical learning for multi- topic text categorization (MTC), whose goal is to choose all relevant top- ics (a label) from a given set of topics. The proposed algorithm, Max- imal Margin Labeling (MML), treats all possible labels as independent classes and learns a multi-class classifier on the induced multi-class cate- gorization problem. To cope with the data sparseness caused by the huge number of possible labels, MML combines some prior knowledge about label prototypes and a maximal margin criterion in a novel way. Experi- ments with multi-topic Web pages show that MML outperforms existing learning algorithms including Support Vector Machines. This paper addresses the problem of learning for multi-topic text categorization (MTC), whose goal is to select all topics relevant to a text from a given set of topics.
Consistency of one-class SVM and related algorithms
We determine the asymptotic limit of the function computed by support vector machines (SVM) and related algorithms that minimize a regularized empirical convex loss function in the reproducing kernel Hilbert space of the Gaussian RBF kernel, in the situation where the number of examples tends to infinity, the bandwidth of the Gaussian kernel tends to 0, and the regularization parameter is held fixed. Non-asymptotic convergence bounds to this limit in the L2 sense are provided, together with upper bounds on the classification error that is shown to converge to the Bayes risk, therefore proving the Bayes-consistency of a variety of methods although the regularization term does not vanish. These results are particularly relevant to the one-class SVM, for which the regularization can not vanish by construction, and which is shown for the first time to be a consistent density level set estimator.