结合支持向量机与半监督K-means的新型学习算法

半监督学习结合少量有标签样本和大量无标签样本,可以有效提高算法的泛化性能。传统的半监督支持向量机（SVM）算法在目标函数中引入无标签样本的依赖项来推动决策面通过低密度区域,但往往会带来高计算复杂度和局部最优解等问题。同时,半监督K-means算法面临着如何有效利用监督信息进行质心的初始化及更新等问题。针对上述问题,提出了一种结合SVM和半监督K-means的新型学习算法（SKAS）。首先,提出一种改进的半监督K-means算法,从距离度量和质心迭代两个方面进行了改进;然后,设计了一种融合算法将半监督K-means算法与SVM相结合以进一步提升算法性能。在6个UCI数据集上的实验结果表明,所提算法在其中5个数据集上的运行结果都优于当前先进的半监督SVM算法和半监督K-means算法,且拥有最高的平均准确率。     

基于交叉熵的安全Tri-training算法

半监督学习方法通过少量标记数据和大量未标记数据来提升学习性能.Tri-training是一种经典的基于分歧的半监督学习方法,但在学习过程中可能产生标记噪声问题.为了减少Tri-training中的标记噪声对未标记数据的预测偏差,学习到更好的半监督分类模型,用交叉熵代替错误率以更好地反映模型预估结果和真实分布之间的差距,并结合凸优化方法来达到降低标记噪声的目的,保证模型效果.在此基础上,分别提出了一种基于交叉熵的Tri-training算法、一个安全的Tri-training算法,以及一种基于交叉熵的安全Tri-training算法.在UCI(University of California Irvine)机器学习库等基准数据集上验证了所提方法的有效性,并利用显著性检验从统计学的角度进一步验证了方法的性能.实验结果表明,提出的半监督学习方法在分类性能方面优于传统的Tri-training算法,其中基于交叉熵的安全Tri-training算法拥有更高的分类性能和泛化能力.     

基于分类的半监督聚类方法

提出一种基于分类的半监督聚类算法。充分利用了数据集中的少量标记对象对原始数据集进行粗分类,在传统k均值算法的基础上扩展了聚类中心点的选择方法;用k-meansGuider方法对数据集进行粗聚类,在此基础上对粗聚类结果进行集成。在多个UCI标准数据集上进行实验,结果表明提出的算法能有效改善聚类质量。     

使用模拟切削算法的SVM增量学习机制

提出使用模拟切削算法的SVM增量学习机制。模拟切削算法在核函数映射的特征空间中计算每个样本的预期贡献率, 仅选取预期贡献率较高的样本参与SVM增量学习, 有效解决传统SVM增量学习代价高、目标样本选取准确性低、分类器缺乏鲁棒性的问题。一个样本的预期贡献率采用通过该样本的映射目标的合适分离面对两类样本的识别率来表示。对目标样本的选取酷似果蔬削皮的过程, 所提算法由此得名。基准数据实验表明, 文中算法在学习效率和分类器泛化性能上具有突出优势。在有限资源学习问题上的应用表明该算法在大规模学习任务上的良好性能。     

Genetic algorithm–based training for semi-supervised SVM

The Support Vector Machine (SVM) is an interesting classifier with excellent power of generalization. In this paper, we consider applying the SVM to semi-supervised learning. We propose using an additional criterion with the standard formulation of the semi-supervised SVM (S ³ VM) to reinforce classifier regularization. Since, we deal with nonconvex and combinatorial problem, we use a genetic algorithm to optimize the objective function. Furthermore, we design the specific genetic operators and certain heuristics in order to improve the optimization task. We tested our algorithm on both artificial and real data and found that it gives promising results in comparison with classical optimization techniques proposed in literature.     

用LDL~T并行分解优化大规模SVM的训练效率

支持向量机在大规模训练集上学习时,存在学习时间长、泛化能力下降的问题。研究使用路径跟踪内点法构建面向大规模训练集的SVM学习算法,找到影响算法学习效率的关键是求解大型线性修正方程,首先使用降维法降低修正方程的维数,再使用矩阵LDLT并行分解高效地求解子修正方程,达到优化大规模SVM学习效率的目的,实验结果说明SVM训练效率提升的同时不影响SVM模型的泛化能力。     

An adaptive class pairwise dimensionality reduction algorithm

Support vector machines (SVM) has achieved great success in multi-class classification. However, with the increase in dimension, the irrelevant or redundant features may degrade the generalization performances of the SVM classifiers, which make dimensionality reduction (DR) become indispensable for high-dimensional data. At present, most of the DR algorithms reduce all data points to the same dimension for multi-class datasets, or search the local latent dimension for each class, but they neglect the fact that different class pairs also have different local latent dimensions. In this paper, we propose an adaptive class pairwise dimensionality reduction algorithm (ACPDR) to improve the generalization performances of the multi-class SVM classifiers. In the proposed algorithm, on the one hand, different class pairs are reduced to different dimensions; on the other hand, a tabu strategy is adopted to select adaptively a suitable embedding dimension. Five popular DR algorithms are employed in our experiment, and the numerical results on some benchmark multi-class datasets show that compared with the traditional DR algorithms, the proposed ACPDR can improve the generalization performances of the multi-class SVM classifiers, and also verify that it is reasonable to consider the different class pairs have different local dimensions.     

Evolutionary strategies for hyperparameters of support vector machines based on multi-scale radial basis function kernels

Kernel functions are used in support vector machines (SVM) to compute inner product in a higher dimensional feature space. SVM classification performance depends on the chosen kernel. The radial basis function (RBF) kernel is a distance-based kernel that has been successfully applied in many tasks. This paper focuses on improving the accuracy of SVM by proposing a non-linear combination of multiple RBF kernels to obtain more flexible kernel functions. Multi-scale RBF kernels are weighted and combined. The proposed kernel allows better discrimination in the feature space. This new kernel is proved to be a Mercer’s kernel. Furthermore, evolutionary strategies (ESs) are used for adjusting the hyperparameters of SVM. Training accuracy, the bound of generalization error, and subset cross-validation on training accuracy are considered to be objective functions in the evolutionary process. The experimental results show that the accuracy of multi-scale RBF kernels is better than that of a single RBF kernel. Moreover, the subset cross-validation on training accuracy is more suitable and it yields the good results on benchmark datasets.     

基于混合样本自动数据增强技术的半监督学习方法

基于一致性的半监督学习方法通常使用简单的数据增强方法来实现对原始输入和扰动输入的一致性预测.在有标签数据的比例较低的情况下,该方法的效果难以得到保证.将监督学习中一些先进的数据增强方法扩展到半监督学习环境中,是解决该问题的思路之一.基于一致性的半监督学习方法MixMatch,提出了基于混合样本自动数据增强技术的半监督学...     

基于边界样本选择的支持向量机加速算法

针对支持向量机（Support Vector Machine,SVM）处理大规模数据集的学习时间长、泛化能力下降等问题,提出基于边界样本选择的支持向量机加速算法。首先,进行无监督的K均值聚类;然后,在各个聚簇内依照簇的混合度、支持度因素应用K近邻算法剔除非边界样本,获得最终的类别边界区域样本,参与SVM模型训练。在标准数据集上的实验结果表明,算法在保持传统支持向量机的分类泛化能力的同时,显著降低了模型训练时间。     

The robust and efficient adaptive normal direction support vector regression

The recently proposed reduced convex hull support vector regression (RH-SVR) treats support vector regression (SVR) as a classification problem in the dual feature space by introducing an epsilon-tube. In this paper, an efficient and robust adaptive normal direction support vector regression (AND-SVR) is developed by combining the geometric algorithm for support vector machine (SVM) classification. AND-SVR finds a better shift direction for training samples based on the normal direction of output function in the feature space compared with RH-SVR. Numerical examples on several artificial and UCI benchmark datasets with comparisons show that the proposed AND-SVR derives good generalization performance     

基于局部尺度转换的拉普拉斯核方法

采用数据点的结构信息可以提高半监督学习的性能。为此,提出一种基于图的半监督学习方法。利用局部尺度转换对不同密度区域中的边权重设置不同的尺度参数,在此基础上构造图的拉普拉斯核分类器进行分类学习。在多个数据集上的实验显示该方法优于其他基于核的半监督分类方法。     

基于Fisher 准则和最大熵原理的SVM核参数选择方法

针对支持向量机(SVM)核参数选择困难的问题,提出一种基于Fisher准则和最大熵原理的SVM核参数优选方法.首先,从SVM分类器原理出发,提出SVM核参数优劣的衡量标准;然后,根据此标准利用Fisher准则来优选SVM核参数,并引入最大熵原理进一步调整算法的优选性能.整个模型采用粒子群优化算法(PSO)进行参数寻优.UCI标准数据集实验表明了所提方法具有良好的参数选择效果,优选出的核参数能够使SVM具有较高的泛化性能.     

基于两阶段学习的半监督支持向量机分类算法

提出了一种基于两阶段学习的半监督支持向量机(semi-supervised SVM)分类算法.首先使用基于图的标签传递算法给未标识样本赋予初始伪标识,并利用k近邻图将可能的噪声样本点识别出来并剔除;然后将去噪处理后的样本集视为已标识样本集输入到支持向量机(SVM)中,使得SVM在训练时能兼顾整个样本集的信息,从而提高SVM的分类准确率.实验结果证明,同其它半监督学习算法相比较,本文算法在标识的训练样本较少的情况下,分类性能有所提高且具有较高的可靠性.     

正则化路径上的支持向量机模型组合方法

模型组合是提高支持向量机泛化性的重要方法,但存在计算效率较低的问题。提出一种基于正则化路径上贝叶斯模型平均的支持向量机模型组合方法,在提高支持向量机泛化性的同时,具有较高的计算效率。基于正则化路径算法建立初始模型集,引入对支持向量机的概率解释。模型的先验可看做是一个高斯过程,模型的后验概率通过贝叶斯公式求得,使用贝叶斯模型平均对模型进行组合。在标准数据集上,实验比较了所提出的模型组合方法与交叉验证及广义近似交叉验证（GACV）方法的性能,验证所提出的模型组合方法的有效性。     

快速支持向量机增量学习算法

支持向量机对数据的学习往往因为规模过大造成学习困难,增量学习通过把数据集分割成历史样本集和新增样本集,利用历史样本集的几何分布信息,通过定义样本的遗忘因子,提取历史样本集中的那些可能成为支持向量的边界向量进行初始训练.在增量学习过程中对学习样本的知识进行积累,有选择地淘汰学习样本.实验结果表明,该算法在保证学习的精度和推广能力的同时,提高了训练速度,适合于大规模分类和在线学习问题.     

Approximating support vector machine with artificial neural network for fast prediction

Support vector machine (SVM) is a powerful algorithm for classification and regression problems and is widely applied to real-world applications. However, its high computational load in the test phase makes it difficult to use in practice. In this paper, we propose hybrid neural network (HNN), a method to accelerate an SVM in the test phase by approximating the SVM. The proposed method approximates the SVM using an artificial neural network (ANN). The resulting regression function of the ANN replaces the decision function or the regression function of the SVM. Since the prediction of the ANN requires significantly less computation than that of the SVM, the proposed method yields faster test speed. The proposed method is evaluated by experiments on real-world benchmark datasets. Experimental results show that the proposed method successfully accelerates SVM in the test phase with little or no prediction loss.     

基于最小二乘支持向量机的航煤干点软测量应用研究

传统支持向量机是近几年发展起来的一种基于统计学习理论的学习机器,在非线性函数回归估计方面有许多应用。最小二乘支持向量机用等式约束代替传统支持向量机方法中的不等式约束,利用求解一组线性方程得出对象模型,避免了求解二次规划问题。本文采用最小二乘支持向量机解决了航空煤油干点的在线估计问题,结果表明,最小二乘支持向量机学习速度快、精度高,是一种软测量建模的有效方法。在相同样本条件下,比RBF网络具有较好的模型逼近性和泛化性能,比传统支持向量机可节省大量的计算时间。     

基于正则化路径的支持向量机近似模型选择

模型选择问题是支持向量机的基本问题.基于核矩阵近似计算和正则化路径,提出一个新的支持向量机模型选择方法.首先,发展初步的近似模型选择理论,包括给出核矩阵近似算法KMA-α,证明KMA-α的近似误差界定理,进而得到支持向量机的模型近似误差界.然后,提出近似模型选择算法AMSRP.该算法应用KMA-α计算的核矩阵的低秩近似来提高支持向量机求解的效率,同时应用正则化路径算法来提高惩罚因子C参数调节的效率.最后,通过标准数据集上的对比实验,验证了AMSRP的可行性和计算效率.实验结果显示,AMSRP可在保证测试集准确率的前提下,显著地提高支持向量机模型选择的效率.理论分析与实验结果表明,AMSRP是一合理、高效的模型选择算法.     

A rough margin-based one class support vector machine

We propose a rough margin-based one class support vector machine (Rough one class SVM) by introducing the rough set theory into the one class SVM, to deal with the over-fitting problem. We first construct rough lower margin, rough upper margin, and rough boundary and then maximize the rough margin rather than the margin in the one class SVM. Thus, more points are adaptively considered in constructing the separating hyper-plane than those used in the conventional one class SVM. Moreover, different points staying at the different positions are proposed to give different penalties. Specifically, the samples staying at the lower margin are given the larger penalties than those in the boundary of the rough margin. Therefore, the new classifier can avoid the over-fitting problem to a certain extent and yields great generalization performance. Experimental results on one artificial dataset and eight benchmark datasets demonstrate the feasibility and validity of our proposed algorithm.