关于主成分分析综合评价函数质疑的讨论

主成分分析综合评价是国内较流行的一种综合评价方法,这里对主成分分析综合评价函数的五个质疑或断言,用主成分分析模型、主成分分析综合评价的合理性条件进行了讨论,结果:主成分分析综合评价函数是果,主成分及其包含的信息是因,不能用它们包含的信息比较后推断,因果关联的它们既应分别深入分析,又应结合分析,效果会更好.并结合实例说明:具有合理性条件的主成分分析综合评价改进步骤,更具有合理性和有效性.     

对主成分分析法三个问题的剖析

从主成分分析法的基本原理入手,针对教学过程中学生对主成分分析法感到费解的三个问题进行了逐一剖析:1.为什么主成分系数是经标准差标准化后原始变量的协方差矩阵的特征向量?2.特征向量正负号如何选取?对进一步的研究如计算综合得分和聚类分析有何影响?3.主成分载荷值是如何得来的?同时指出有些教材在计算主成分得分时混淆了主成分载荷和特征向量的概念,以致造成错误的结果.     

用主成分分析法作多指标综合评价应该注意的问题

主成分分析法是一种很好的多指标综合评价方法,但须注意其适用性,也要对评价结果恰当地使用.如果样本太少,或者各变量之间的相关性很小,则不适合使用;涉及到动态的价值型的指标评价问题必须作不变价在处理;如果仅仅是进行排序评价则只用一个主成分得分进行评价即可;若还要进行其他方面的分析,则在选取主成分个数时,只能选取特征根大于1所对应主成分;计算各样本的主成分得分一定要采取变权的方式进行;在对各主成分进行命名和特征概括时要首先考察各变量在不同主成分载荷的绝对值大小,在此基础上选择同一主成分上载荷较大的变量主成分命名和特征概括;如果要做倍比分析,则要把各样本的主成分得分映射到适当的正数区间,该区间的选择需要一定的经验,或者参照其他指标的倍比关系确定.     

稳健稀疏主成分分析法及其实证研究

主成分分析是多元统计分析中一种非常经典的降维技术。然而,经典主成分分析却是对离群值非常敏感的,常因离群值的存在导致结果与实际不相符。另一方面,当主成分分析用于综合评价时,主成分的含义常因载荷间绝对值大小不分明而含糊不清,从而导致综合评价难以展开。本文通过使用稳健稀疏主成分分析法进行模拟实验和实证分析,结果表明:该方法不仅能很好地抵抗离群值的影响,而且还能准确地识别出离群样本。通过该方法得出的主成分的含义也较经典主成分分析和稳健主成分分析更加地明确和贴近实际。     

对称设计与主成分分析

在科学研究中,经常利用观测到的数据研究复杂系统的主要成分与观测变量的关系,这实际上是科学的最基础问题之一,称为"主成分分析".对"主成分分析"的优良性研究文章众多,但是由于东西方认知世界的哲学思想不同,所以历史上东西方对"主成分分析"的计算和论证方法有着相当大的差异.利用对称设计对数据进行分类,通过对东西方主成分分析的计算方法进行比较,说明东方象数学的主成分分析的计算方法具有再现性,而西方主成分分析的计算方法不具有再现性.从再现性的观点来看,东方象数学的主成分分析的计算方法科学性更强.     

基于主成分分析的建筑工程成本影响因素分析

影响建筑工程成本的因素众多,这些因素在某种程度上是相关联的,甚至有些是冗余的.运用主成分分析法对影响建筑工程成本的因素进行归纳分析,将影响建筑工程成本17个因素通过主成分分析用5个主成分表示并构造出影响建筑工程成本的主成分综合评价函数,使在工程成本领域多维指标实现综合分析得以实现,为建筑工程成本的研究提供参考.     

主成分分析在环境质量评价中的失效问题

在环境质量评价中,主成分分析被认为是一种客观而实用的评价方法.但大量的数据分析表明,主成分分析的评价结果并不一定符合实际情况,有时甚至完全失效,存在着一系列问题,而这些问题是由主成分分析本身的性质所决定的.     

对台湾工农业产品产量的主成分分析

主成分析分析法是一种将多个指标化为少数几个不相关的综合指标 (即主成分 )的多元统计分析方法 .本文通过运用主成分方法对我国台湾地区 1 989 1 996工农业主要指标的原始数据的处理分析 ,表明主成分分析确是在实用中很可行的一种常用的统计方法 .     

学生成绩的学分绩与主成分排序模型

利用多元统计中的主成分分析研究学生成绩,发现第一主成分排序与学分绩排序结果基本相同,提出用第一主成分代替学分绩对学生进行综合评价更加合理.而且主成分还能反映教学过程中的优点和不足.对教学有一定的指导意义.     

基于主成分——BP神经网络的期货市场预测

结合主成分分析法和神经网络的优点,提出了基于主成分分析的神经网络方法来对期货市场进行预测.引入主成分分析法对原始输入变量进行预处理,选择输入变量的主成分作为网络输入,一方面减少了输入维度,消除了各输入变量的相关性;另一方面提高了网络的收敛性和稳定性,也简化了网络的结构.通过实例验证,基于主成分的神经网络比一般神经网络训练精度更高.     

Hypersurfaces of the hyperbolic space with constant scalar curvature

We classify hypersurfaces of the hyperbolic space ?ⁿ⁺¹(c) with constant scalar curvature and with two distinct principal curvatures. Moreover, we prove that if Mⁿ is a complete hypersurfaces with constant scalar curvature n(n ? 1) R and with two distinct principal curvatures such that the multiplicity of one of the principal curvatures is n? 1, then R ≥ c. Additionally, we prove two rigidity theorems for such hypersurfaces.     

A note on the commutativity of groups

In this article, we show that a group is abelian if and only if every two elements of the same order commute.     

On the algebraic relation between principal components corresponding to two different sets of weights

In principal component analysis, it is sometimes useful to give weights to observations. When two different sets of weights are attached to the observations of a data table, we derive the algebraic relation between the corresponding two principal component matrices.     

Some New Results on the Eigenvector Centrality

In this article we establish new results on the components of the principal eigenvector in an undirected graph. Those results are particularly significant in relation to the concept of centrality in social networks. In particular degree centrality and eigenvector centrality are compared. We find further conditions, based on the spectral radius, on which nodes with highest degree centrality are also the most eigencentral.     

The Dirichlet problem for the Bellman equation at resonance

We generalize the Donsker-Varadhan minimax formula for the principal eigenvalue of a uniformly elliptic operator in nondivergence form to the first principal half-eigenvalue of a fully nonlinear operator which is concave (or convex) and positively homogeneous. Examples of such operators include the Bellman operator and the Pucci extremal operators. In the case that the two principal half-eigenvalues are not equal, we show that the measures which achieve the minimum in this formula provide a partial characterization of the solvability of the corresponding Dirichlet problem at resonance.     

Real Hypersurfaces with Two Principal Curvatures in Complex Projective and Hyperbolic Planes

We find the first examples of real hypersurfaces with two nonconstant principal curvatures in complex projective and hyperbolic planes, and we classify them. It turns out that each such hypersurface is foliated by equidistant Lagrangian flat surfaces with parallel mean curvature or, equivalently, by principal orbits of a cohomogeneity two polar action.     

Minimal cubature formulae of trigonometric degree

In this paper we construct minimal cubature formulae of trigonometric degree: we obtain explicit formulae for low dimensions of arbitrary degree and for low degrees in all dimensions. A useful tool is a closed form expression for the reproducing kernels in two dimensions.

     

On Hypersurfaces of Spheres with Two Principal Curvatures

In this paper we obtain a classification of hypersurfaces in the Euclidean sphere having two principal curvatures; for some of the results we impose that the sectional curvature (Ricci curvature, resp.) is non-negative Ricci.     

Positive solutions for a Lotka-Volterra prey-predator model with cross-diffusion and Holling type-Ⅱ functional response

We consider a Lotka-Volterra prey-predator model with cross-diffusion and Holling type-II functional response.The main concern is the existence of positive solutions under the combined effect of cross-diffusion and Holling type-II functional response.Here,a positive solution corresponds to a coexistence state of the model.Firstly,we study the sufficient conditions to ensure the existence of positive solutions by using degree theory and analyze the coexistence region in parameter plane.In addition,we present the uniqueness of positive solutions in one dimension case.Secondly,we study the stability of the trivial and semi-trivial solutions by analyzing the principal eigenvalue of the corresponding linearized system,and then we characterize the stable/unstable regions of semi-trivial solutions in parameter plane.