R语言基础

##数据获取

x1=round(runif(100,min=80,max=100))

x2=round(rnorm(100,mean=80, sd=7))

x3=round(rnorm(100,mean=80,sd=18))

x3[which(x3>100)]=100

num=seq(2005138101,length=100)

x=data.frame(num,x1,x2,x3)

write.table(x, "grade.txt")

##数据分析

y=read.table("grade.txt")

mean(y)

colMeans(y)

colMeans(y)(c("x1","x2","x3"))

#//2代表按列取平均值

apply(x, 2, mean)

apply(x, 2, max)

apply(x, 2, min)

apply(x[c("x1","x2","x3")], 2, sum)

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