基于概率投票策略的多类支持向量机及应用

传统的支持向量机是基于两类问题提出的,如何将其有效地推广至多类分类仍是一个研究的热点问题。在分析比较现有支持向量机多类分类OVO方法存在的问题及缺点的基础上,该文提出一种新的基于概率投票策略的多类分类方法。在该策略中,充分考虑了OVO方法中各个两类支持向量机分类器的差异,并将该差异反映到投票分值上。所提多类支持向量机方法不仅具有较好的分类性能,而且有效解决了传统投票策略中存在的拒分区域问题。将基于概率投票的多分类支持向量机作为关键技术应用于实际齿轮箱故障诊断,并与传统投票策略的结果进行对比,表明所提方法的上述优点。     

一种新的基于二叉树的SVM多类分类方法

介绍了几种常用的支持向量机多类分类方法,分析其存在的问题及缺点。提出了一种基于二叉树的支持向量机多类分类方法（BT SVM）,并将基于核的自组织映射引入进行聚类。结果表明,采用该方法进行多类分类比1 v r SVMs和1 v 1 SVMs具有更高的分类精度。     

多类支持向量机方法的研究现状与分析

支持向量机（SVM）是建立在统计学理论基础上的一种小样本机器学习方法，最初应用于解决两类分类问题．然而在解决实际问题中遇到的多为多分类问题，如何有效的将其推广到多类分类问题是一个正在研究的问题．该文对现有的多类支持向量机方法从组合多个两类分类器、层次结构、一次性优化问题和纠错编码等4个角度进行了综合归纳和分析，详细介绍了每种方法的代表性算法，并比较其优劣．     

多类支持向量机在文本分类中的应用

传统的支持向量机（SVM）是两类分类问题,如何有效地将其推广到多类分类问题仍是一项有待研究的课题。本文在对现有主要的四种多类支持向量机分类算法讨论的基础上,结合文本分类的特点,详细介绍了决策树支持向量机和几种改进多类支持向量机方法在文本分类中的应用。     

多类支持向量机分类器对比研究

为了解决多类支持向量机的选型问题,降低多类分类问题的难度,对4种常用的多类支持向量机进行了对比研究。从多类支持向量机的构造原理出发,对多类支持向量机的训练复杂度、测试复杂度和分类准确率进行了理论分析。在此基础上,利用标准数据集对多类支持向量机进行试验分析,结果表明,导向无环图支持向量机的分类准确率最高,二叉树支持向量机的实时性最优。     

多类支持向量机文本分类方法

文本分类是数据挖掘的基础和核心,支持向量机(SVM)是解决文本分类问题的最好算法之一.传统的支持向量机是两类分类问题,如何有效地将其推广到多类分类问题仍是一项有待研究的课题.介绍了支持向量机的基本原理,对现有主要的多类支持向量机文本分类算法进行了讨论和比较.提出了多类支持向量机文本分类中存在的问题和今后的发展.     

一种基于类中心最大间隔的支持向量机

传统的支持向量机分类超平面对噪声和野值非常敏感．使用传统的支持向量机对含有噪声的数据分类时，所得到的超平面往往不是最优超平面．为了解决这个问题，本文以两个类中心距离最大为准则建立分类超平面，构造一个新的支持向量机,称作类中心最大间隔支持向量机．理论分析和仿真实验结果证明了该方法的正确性和有效性．     

支持向量机多类分类算法新研究

支持向量机最初是针对两类分类问题提出的,如何将其推广至多类分类问题是当前SVM研究中的热点问题之一。主要针对支持向量机多类分类方法中的分解重构法进行了深入分析,详细讨论了影响分类器性能的两个关键因素：分解策略和组合策略,并通过实验验证了该观点。最后,通过实验对比了包括M-ary 支持向量机和模糊支持向量机的SVM多类分类方法。     

多类支持向量机文本分类方法

文本分类是数据挖掘的基础和核心,支持向量机（SVM）是解决文本分类问题的最好算法之一。传统的支持向量机是两类分类问题,如何有效地将其推广到多类分类问题仍是一项有待研究的课题。介绍了支持向量机的基本原理,对现有主要的多类支持向量机文本分类算法进行了讨论和比较。提出了多类支持向量机文本分类中存在的问题和今后的发展。     

基于超球体的二叉树SVM多分类算法的研究

针对现有的支持向量机在多类分类方法上存在的不足,提出了一种基于超球体的二叉树SVM多类分类算法。该算法利用球结构的SVM考虑了每个类的分布情况,能有效地处理不平衡样本数据,设计超球体支持向量机的树型模型,克服了差错积累问题。实验证明,与其它SVM多类分类方法相比,该方法具有较高的分类精度,提高了支持向量机在多类分类问题中的实验效果。     

A Novel and Principled Multiclass Support Vector Machine

Support vector machines (SVMs) have been demonstrated very efficient for binary classification problems; however, computationally efficient and effective multiclass SVMs are still missing. Most existing multiclass SVM classifiers are constructed either by combining multiple binary SVM classifiers, which often perform moderately for some problems, or by converting multiclass problems into one single optimization problem, which is unfortunately computationally expensive. To address these issues, a novel and principled multiclass SVM based on geometric properties of hyperspheres, termed SVMGH, is proposed in this paper. Different from existing SVM‐based methods that seek a cutting hyperplane between two classes, SVMGH draws the discriminative information of each class by constructing a minimum hypersphere containing all class members, and then defines a label function based on the geometric properties of the minimum hyperspheres. We prove theoretically the geometric properties of the minimum hyperspheres to guarantee the validation of SVMGH. The computational efficiency is enhanced by a data reduction strategy as well as a fast training method. Experimental results demonstrate that the proposed SVMGH shows better performance and higher computational efficiency than the state of the art on multiclassification problems while maintaining comparable performance and efficiency on binary classification problems.     

DESIGN OF DECISION TREE VIA KERNELIZED HIERARCHICAL CLUSTERING FOR MULTICLASS SUPPORT VECTOR MACHINES

As a very effective method for universal purpose pattern recognition, support vector machine (SVM) was proposed for dichotomic classification problem, which exhibits a remarkable resistance to overfitting, a feature explained by the fact that it directly implements the principle of structural risk minimization. However, in real world, most of classification problems consist of multiple categories. In an attempt to extend the binary SVM classifier for multiclass classification, decision-tree-based multiclass SVM was proposed recently, in which the structure of decision tree plays an important role in minimizing the classification error. The present study aims at developing a systematic way for the design of decision tree for multiclass SVM. Kernel-induced distance function between datasets was discussed and then kernelized hierarchical clustering was developed and used in determining the structure of decision tree. Further, simulation results on satellite image interpretation show the superiority of the proposed classification strategy over the conventional multiclass SVM algorithms.     

A new fast algorithm for multiclass hyperspectral image classification with SVM

The support vector machine (SVM) has been a dominant machine-learning technique in the last decade and has demonstrated its efficiency in many applications. Research on classification of hyperspectral images have shown the efficiency of this method to overcome the Hughes phenomenon for classification of such images. A major drawback of classification by SVM is that this classifier was originally developed to solve binary problems, and the algorithms for multiclass problems usually have a high-computational load. In this article, a new and fast method for multiclass problems is proposed. This method has two stages. In the first stage, samples are classified by a maximum likelihood (ML) classifier, and in the second stage, SVM selects the final label of a sample among high-probability classes for that sample by a tree structure. So, for each sample, only some classes must be searched by SVM to find its label. The uncertainty of ML classification for a sample is obtained by the entropy of probabilities, and the number of classes that must be searched by SVM for a sample is obtained based on the uncertainty of that sample in the primary ML classification. This approach is compared with two widely used multiclass algorithms: one-against-one (OAO) and directed acyclic graph (DAGSVM). The obtained results on real data from the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) revealed less computational time and better accuracy compared to these multiclass algorithms.     

基于二叉树的多分类SVM算法在电子邮件过滤中的应用

目前性能较好的多分类算法有1-v-r支持向量机（SVM）、1-1-1SVM、DDAG SVM等，但存在大量不可分区域且训练时间较长的问题。提出一种基于二叉树的多分类SVM算法用于电子邮件的分类与过滤，通过构建二叉树将多分类转化为二值分类，算法采用先聚类再分类的思想，计算测试样本与子类中心的最大相似度和子类间的分离度，以构造决策节点的最优分类超平面。对于C类分类只需C-1个决策函数，从而可节省训练时间。实验表明，该算法得到了较高的查全率、查准率。     

基于混合粒子群算法的运动估计研究

针对块匹配运动估计算法中传统搜索方法的不足,提出了一种新的基于混合粒子群的块匹配运动估计算法。在保留系统随机搜索性能的同时根据运动矢量特性合理地设计初始搜索种群,并通过混沌差分进化搜索协同粒子群算法迭代寻优,混沌序列用于优化差分变异算子,以提高算法的精细搜索能力。通过相同点检测技术和恰当的终止计划有效地降低了系统的运算复杂度。经实验测试与验证,该算法在搜索质量和运算复杂度中达到了一种动态平衡的状态,其整体性能高于传统的快速运动估计算法,效果更逼近于穷举搜索法。     

A comparison of methods for multiclass support vector machines

Support vector machines (SVMs) were originally designed for binary classification. How to effectively extend it for multiclass classification is still an ongoing research issue. Several methods have been proposed where typically we construct a multiclass classifier by combining several binary classifiers. Some authors also proposed methods that consider all classes at once. As it is computationally more expensive to solve multiclass problems, comparisons of these methods using large-scale problems have not been seriously conducted. Especially for methods solving multiclass SVM in one step, a much larger optimization problem is required so up to now experiments are limited to small data sets. In this paper we give decomposition implementations for two such "all-together" methods. We then compare their performance with three methods based on binary classifications: "one-against-all," "one-against-one," and directed acyclic graph SVM (DAGSVM). Our experiments indicate that the "one-against-one" and DAG methods are more suitable for practical use than the other methods. Results also show that for large problems methods by considering all data at once in general need fewer support vectors.     

基于核聚类方法的多层次支持向量机分类树

针对解决多类模式识别问题的SVM方法进行研究。在比较几种常用的多类SVM分类算法的基础上，提出一种基于核聚类方法的多层次SVM分类树，将核空问中的无监督学习方法和有监督学习方法结合起来，实现了一种结构更加简洁清晰、计算效率更高的多层SVM分类树算法，并在实验中取得了良好的结果．     

Fast Multiclass SVM Classification Using Decision Tree Based One-Against-All Method

We present an improved version of One-Against-All (OAA) method for multiclass SVM classification based on a decision tree approach. The proposed decision tree based OAA (DT-OAA) is aimed at increasing the classification speed of OAA by using posterior probability estimates of binary SVM outputs. DT-OAA decreases the average number of binary SVM tests required in testing phase to a greater extent when compared to OAA and other multiclass SVM methods. For a balanced multiclass dataset with K classes, under best situation, DT-OAA requires only (K + 1)/2 binary tests on an average as opposed to K binary tests in OAA; however, on imbalanced multiclass datasets we observed DT-OAA to be much faster with proper selection of order in which the binary SVMs are arranged in the decision tree. Computational comparisons on publicly available datasets indicate that the proposed method can achieve almost the same classification accuracy as that of OAA, but is much faster in decision making.     

快速的支持向量机多类分类研究

研究了支持向量机多类算法DAGSVM（Direct Acyclic Graph SVM）的速度优势,提出了结合DAGSVM和简化支持向量技术的一种快速支持向量机多类分类方法。该方法一方面减少了一次分类所需的两类支持向量机的数量,另一方面减少了支持向量的数量。实验采用UCI和Statlog数据库的多类数据,并和四种多类方法进行比较,结果表明该方法能有效地加快分类速度。