基于核函数的混合C均值聚类算法

提出了一种基于核函数的混合C均值聚类算法.首先利用模糊C均值聚类算法和另一种类型的可能性C均值聚类算法的优点,设计出一种混合C均值聚类算法.然而鉴于该算法存在的不足,本文将Mercer核函数引入到该算法中,仿真实验结果证实了该方法的可行性和有效性.     

一种基于核的混合c-均值聚类模型

FCM和PCM的混合模型可以克服它们单独聚类时的缺点,在聚类效果上有很大改进,但是对于特征不明显的样本而言,这种混合模型的聚类效果并不太好,为了克服这一缺点,本文引入Mercer核,提出了一种新的基于核的混合c-均值聚类模型(KIPCM),运用核函数使得在原始空间不可分的数据点在核空间变得可分。通过数值实验,得到了较为合理的中心值以及较高的正确分类率,证实了本文算法的可行性和有效性。     

基于核方法的数据描述及其在企业关系评价中的应用

数据描述又称为一类分类方法,用于描述现有数据的分布特征,以研究待测试数据是否与该分布相吻合.首先简要叙述了基于核方法的数据描述原理,指出:选择适当的核函数以及与之对应的参数,数据描述可应用于模式聚类中,并且这种聚类方法具有边界紧致、易剔除噪声的优势.针对基于数据描述的聚类方法在确定类别数目和具体样本类别归属上所存在的问题,提出了基于搜索的解决方法,理论分析和实例计算都验证了该方法的可行性.最后将该聚类算法应用到企业关系评价中,取得了较为合理的结果.     

一种基于核密度聚类的电力负荷模式精细化识别算法研究

密度峰值聚类算法(DPC)是一种基于密度的非监督学习算法.分析用电类型复杂的电力负荷数据集时,存在负荷曲线聚类效果过分依赖人为参数设定和无法识别潜在用电模式的缺陷.结合非参数核密度估计,使用带宽搜索与边界优化提出一种适应多类型复杂用户的电力负荷数据优化聚类算法.在某市10KV真实数据集中进行算法测试,使用Davies-Bouldin有效性指标对比优化前后算法聚类效果.结果表明改进算法在面向用户类型复杂的电力数据集时,能够实现已知用电模式精确识别与潜在用电模式的深度挖掘并显著提高聚类有效性.     

基于遗传模拟退火算法的矢量量化码书设计

首先介绍了遗传算法和模拟退火算法等全局优化算法,并针对遗传算法的早熟现象和容易陷入局部最优的缺点,将模拟退火算法引入到遗传算法中,提出了遗传模拟退火矢量量化码书设计(GSAKVQ)算法.此外,针对基于划分的染色体编码方式的特点,算法提出了新的有效的交叉算子和变异算子.同时,将算法从输入空间映射到特征空间,提出了相应的遗传模拟退火核矢量量化算法,改善了算法在某些数据集上的不足.最后,通过实验表明,GSAKVQ算法,在大部分的数据集上都能取得较好的结果,从而验证了算法在数据聚类问题上的有效性.     

基于核方法的模糊对象语言概念格聚类分析

在现实生活中,存在着大量语言值数据.为了解决在语言环境中不确定信息的聚类问题,本文提出了一种新的机器学习方法,即基于核方法的模糊对象语言概念格聚类分析模型.该模型通过融合层次聚类与概念格聚类的原理,在寻找到层次聚类局部最优层次的同时优化概念格聚类中的概念选择与概念构造问题.具体地,提出模糊对象语言概念格及其相关性质,它...     

模糊集IF-THEN规则的蚁群空间聚类分析

将蚂蚁的拾起和放下对象的行为表示为模糊集.通过模糊集的IF-THEN规则计算蚂蚁执行任务的激励和反应阈值,得到蚂蚁拾起或放下项目的概率,对蚂蚁的行为做出决策,实现对空间数据的聚类.以矿山实际测量数据为空间数据源,采用基本的蚁群聚类算法和模糊蚁群空间聚类算法分别对其进行聚类.通过对这两种算法的实验结果进行分析比较,证明改进后的算法提高了聚类效果.     

面向大数据流的多任务在线学习算法研究

大数据时代背景下,越来越多领域对大数据计算提出了高要求,尤其各行各业产生的大数据更多地是一种动态的流式数据形态,因此,实现实时、快速、高效的大数据流计算与分析日益紧要.在线机器学习算法是解决实时大数据流分析的有效方案.在机器学习算法中,通过核学习能够获得有效的核函数,而所选核函数又对核学习器的性能有很大影响.结合在线机器学习与核函数研究一种适用于大数据流环境下的多任务在线学习算法,探讨了算法过程中可能出现的扰动项,应用数据依赖核的构建方法提高了算法的广泛性.算法不需要对历史数据流进行存储和重新扫描,只需选择一个数据集样本,在分析新的流式大数据时能够在可接受时间内直接将当前核函数更新为最合适的核函数,非常适合应用于流式大数据环境下的核学习问题.     

基于类内类间距离量级平衡的FCM聚类算法设计

类内距离和类间距离数值量级差异性导致两类距离无法直接融合,进而影响了FCM聚类模型设计。首先,本文全面回顾了经典和改进型的FCM聚类模型,构建了类内距离和类间距离迹的关系模型,分别从类内类间距离的变化不一致性和量级差异性两个方面分析了现有FCM聚类模型的不足;其次,运用高斯核距离替代传统的欧式距离来表征类内类间距离,基于最小化类内紧凑度与类间分离度差的思想,设计了类内类间距离平衡方法,提出了一种改进的FCM聚类目标函数与算法;最后,运用算例说明了本方法的有效性和优越性。     

基于云自适应遗传算法的K-means聚类分析

现有的基于遗传算法的K-means聚类算法,利用遗传算法的全局优化性提高了K-means算法的寻优能力,收敛速度却过慢.为了解决上述问题,提出基于云自适应遗传算法的K-means聚类算法,利用云模型云滴的随机性和稳定趋向性设计遗传算法的交叉和变异概率,并在进化过程中引入K均值算子,以克服算法收敛速度过慢的问题.实验比较表明,算法具有较好的全局优化性,且收敛速度较快,提高了聚类算法解决物流管理中数据聚类工作的能力.     

An extension to possibilistic fuzzy cluster analysis

We explore an approach to possibilistic fuzzy clustering that avoids a severe drawback of the conventional approach, namely that the objective function is truly minimized only if all cluster centers are identical. Our approach is based on the idea that this undesired property can be avoided if we introduce a mutual repulsion of the clusters, so that they are forced away from each other. We develop this approach for the possibilistic fuzzy c-means algorithm and the Gustafson–Kessel algorithm. In our experiments we found that in this way we can combine the partitioning property of the probabilistic fuzzy c-means algorithm with the advantages of a possibilistic approach w.r.t. the interpretation of the membership degrees.     

Mixed fuzzy inter-cluster separation clustering algorithm

Based on inter-cluster separation clustering (ICSC) fuzzy inter-cluster separation clustering (FICSC) deals with all the distances between the cluster centers, maximizes these distances and obtains the better performances of clustering. However, FICSC is sensitive to noises the same as fuzzy c-means (FCM) clustering. Possibilistic type of FICSC is proposed to combine FICSC and possibilistic c-means (PCM) clustering. Mixed fuzzy inter-cluster separation clustering (MFICSC) is presented to extend possibilistic type of FICSC because possibilistic type of FICSC is sensitive to initial cluster centers and always generates coincident clusters. MFICSC can produce both fuzzy membership values and typicality values simultaneously. MFICSC shows good performances in dealing with noisy data and overcoming the problem of coincident clusters. The experimental results with data sets show that our proposed MFICSC holds better clustering accuracy, little clustering time and the exact cluster centers.     

On the convergence of some possibilistic clustering algorithms

In this paper, an analysis of the convergence performance is conducted for a class of possibilistic clustering algorithms (PCAs) utilizing the Zangwill convergence theorem. It is shown that under certain conditions the iterative sequence generated by a PCA converges, at least along a subsequence, to either a local minimizer or a saddle point of the objective function of the algorithm. The convergence performance of more general PCAs is also discussed.     

Hybrid possibilistic networks

Possibilistic networks and possibilistic logic are two standard frameworks of interest for representing uncertain pieces of knowledge. Possibilistic networks exhibit relationships between variables while possibilistic logic ranks logical formulas according to their level of certainty. For multiply connected networks, it is well-known that the inference process is a hard problem. This paper studies a new representation of possibilistic networks called hybrid possibilistic networks. It results from combining the two semantically equivalent types of standard representation. We first present a propagation algorithm through hybrid possibilistic networks. This inference algorithm on hybrid networks is strictly more efficient (and confirmed by experimental studies) than the one of standard propagation algorithm.     

A possibilistic mean-semivariance-entropy model for multi-period portfolio selection with transaction costs

This paper deals with a multi-period portfolio selection problem with fuzzy returns. A possibilistic mean-semivariance-entropy model for multi-period portfolio selection is presented by taking into account four criteria viz., return, risk, transaction cost and diversification degree of portfolio. In the proposed model, the return level is quantified by the possibilistic mean value of return, the risk level is characterized by the lower possibilistic semivariance of return, and the diversification degree of portfolio is measured by the originally presented possibilistic entropy. Furthermore, a hybrid intelligent algorithm is designed to obtain the optimal portfolio strategy. Finally, the comparison analysis between the possibilistic entropy model and the proportion entropy model is provided by two numerical examples to illustrate the efficiency of the proposed approaches and the designed algorithm.     

A class of possibilistic portfolio selection model with interval coefficients and its application

Because of the existence of non-stochastic factors in stock markets, several possibilistic portfolio selection models have been proposed, where the expected return rates of securities are considered as fuzzy variables with possibilistic distributions. This paper deals with a possibilistic portfolio selection model with interval center values. By using modality approach and goal attainment approach, it is converted into a nonlinear goal programming problem. Moreover, a genetic algorithm is designed to obtain a satisfactory solution to the possibilistic portfolio selection model under complicated constraints. Finally, a numerical example based on real world data is also provided to illustrate the effectiveness of the genetic algorithm.     

Possibilistic clustering approach to trackless ring Pattern Recognition in RICH counters

The pattern recognition problem in Ring Imaging CHerenkov (RICH) counters concerns the identification of an unknown number of rings whose centers and radii are assumed to be unknown. In this paper we present an algorithm based on the possibilistic approach to clustering that automatically finds both the number of rings and their position without any a priori knowledge. The algorithm has been tested on realistic Monte Carlo LHCb simulated events and it has been shown very powerful in detecting complex images full of rings. The tracking-independent algorithm could be usefully employed after a track based approach to identify remaining trackless rings.     

A cutting plane algorithm for MV portfolio selection model

This paper deals with a portfolio selection problem with fuzzy return rates. A possibilistic mean variance (FMVC) portfolio selection model was proposed. The possibilistic programming problem can be transformed into a linear optimal problem with an additional quadratic constraint by possibilistic theory. For such problems there are no special standard algorithms. We propose a cutting plane algorithm to solve (FMVC). The nonlinear programming problem can be solved by sequence linear programming problem. A numerical example is given to illustrate the behavior of the proposed model and algorithm.     

Possibilistic sequential decision making

When the information about uncertainty cannot be quantified in a simple, probabilistic way, the topic of possibilistic decision theory is often a natural one to consider. The development of possibilistic decision theory has lead to the proposition a series of possibilistic criteria, namely: optimistic and pessimistic possibilistic qualitative criteria [7], possibilistic likely dominance [2], [9], binary possibilistic utility [11] and possibilistic Choquet integrals [24]. This paper focuses on sequential decision making in possibilistic decision trees. It proposes a theoretical study on the complexity of the problem of finding an optimal strategy depending on the monotonicity property of the optimization criteria – when the criterion is transitive, this property indeed allows a polytime solving of the problem by Dynamic Programming. We show that most possibilistic decision criteria, but possibilistic Choquet integrals, satisfy monotonicity and that the corresponding optimization problems can be solved in polynomial time by Dynamic Programming. Concerning the possibilistic likely dominance criteria which is quasi-transitive but not fully transitive, we propose an extended version of Dynamic Programming which remains polynomial in the size of the decision tree. We also show that for the particular case of possibilistic Choquet integrals, the problem of finding an optimal strategy is NP-hard. It can be solved by a Branch and Bound algorithm. Experiments show that even not necessarily optimal, the strategies built by Dynamic Programming are generally very good.