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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
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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
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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
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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
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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
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