过雁

摘要： 概述：余弦相似度 是对两个向量相似度的描述，表现为两个向量的夹角的余弦值。当方向相同时（调度为0），余弦值为1，标识强相关；当相互垂直时（在线性代数里，两个维度垂直意味着他们相互独立），余弦值为0，标识他们无关。Cosine similarityis a measure of similarity between two vectors of aninner product spacetha... 阅读全文

摘要： 1. 定义协同过滤（Collaborative Filtering）有狭义和广义两种意义：广义协同过滤：对来源不同的数据，根据他们的共同点做过滤处理。Collaborative filtering(CF) is a technique used by somerecommender systems.[1]Collaborative filtering has two senses, a n... 阅读全文

摘要： 数学定义[编辑]若k个随机变量、……、是相互独立，符合标准正态分布的随机变量（数学期望为0、方差为1），则随机变量Z的平方和被称为服从自由度为k的卡方分布，记作Definition[edit]IfZ1, ...,Zkareindependent,standard normalrandom variables, then the sum of their squares,is dis... 阅读全文

摘要： 定义：Instatistical surveys, when subpopulations within an overall population vary, it is advantageous to sample each subpopulation (stratum) independently.Stratificationis the process of dividing memb... 阅读全文

摘要： 皮尔森相关系数定义： 协方差与标准差乘积的商。Pearson's correlation coefficient when applied to a population is commonly represented by the Greek letter ρ (rho) and may be referred to as the population correlation coefficie... 阅读全文