R语言中scale函数生成的attr(,"scaled:center")， attr(,"scaled:scale")是什么

 

001、

a <- c(8, 2, 3, 7, 6, 1, 2, 4)
b <- c(2, 3, 6, 2, 6, 9, 3, 7)
c <- c(9, 2, 7, 1, 4, 2, 8, 4)
dat <- data.frame(a, b, c)                    ## 测试数据框
dat
dat2 <- scale(dat, center = T, scale = T)     ## 生成dat2
dat2

attr(dat2,"scaled:center")                    ## 获取每列的均值
attr(dat2,"scaled:scale")                     ## 获取每列的标准差
apply(dat, 2, mean)                           ## 验证
apply(dat, 2, sd)                             ## 验证