一. R的数学函数,统计函数及字符处理函数 例01:一道实际应用题 一组学生其数学,科学和英语的成绩如下表: 任务:根据成绩,决定对每个学生的单独指导: 前20%的学生的成绩为A,次之为B,以此类推: 把学生姓名按照字母表顺序排序. 问题:三科考试的分数不具可比性:必须把考试分数转化为可以比较的记分单元,然后才能进行分数间的比较. 为分配A,B等级,需把学生成绩转换为百分比形式. 姓名有单独的域,使得分配学生的任务变得更难:故应该把名字分为名和姓. 1. 数字和字符函数(Numerical(ma…

二. 控制流 statement:一个单独的R语句或者是一个复合的R语句: cond:条件表达式,为TRUE或FALSE: expr:数字或字符表达式: seq:数字或字符串的顺序. 1.循环语句:for,while (1)for(var in seq)  statement for(i in 1:10) + print("Hello R") [1] "Hello R" [1] "Hello R" [1] "Hello R"…

1. 创建新的变量 variable<-expression expression:包含一组大量的操作符和函数.常用的算术操作符如下表: 例1:根据已知变量,创建新变量的三种途径 > mydata<-data.frame(x1=c(2,2,6,4),x2=c(3,4,2,8)) > mydata$sumx<-mydata$x1+mydata$x2 > mydata$meanx<-(mydata$x1+mydata$x2)/2 >> attach(myd…

原文地址:http://www.javacodegeeks.com/2015/07/mysql-vs-mongodb.html 1. Introduction It would be fair to say that as IT professionals we are living in the golden age of data management era. As our software systems become more complex and more distributed,…

场景3 Data Management 数据管理 性能优化 OLTP OLAP 物化视图 :表的快照 传输表空间 :异构平台的数据迁移 星型转换 :事实表 OLTP : 在线事务处理 1. transaction —> DML 2. 数据量小 3. 处理时间短 —> SQL 共享,绑定变量 4. 并发量大 OLAP,DSS 1. 以查询为主(海量)—> 数据汇总 —> 结果放到表(物化视图)里 2. 处理时间长 3. 几乎无并发 4. 做并行处理 SGA + PGA memory_…

Advanced Data Structures Advanced Data Structures…

http://www.windowsazure.com/en-us/develop/net/fundamentals/cloud-storage/ Managing and analyzing data in the cloud is just as important as it is anywhere else. To let you do this, Windows Azure provides a range of technologies for working with relati…

1.Database concepts (1)Data & Information Information Is any kind of event that affects the state of a dynamic system Is the message (utterance or expression) being conveyed Is an ordered sequence of symbols that can be interpreted as a message As se…

Data Management ObjectivesBy the end o this module, you should understand the fundamentals of data management, including:1.Explain typical data management operations.2.Describe typical user cases for inserting system fields.3.List the ways to obtain…

ev401-018:Data Management: Data management ToolsModule Objectives1.List objects exposed in the import wizards.2.List some objects not exposed in the import wizards.3.List some capabilities of API-based tools that the import wizards do not have.4.Stat…