R中list对象属性以及具有list性质的对象

R语言list的特点：It has length, [[ and [ methods, and is recursive because list can contain other list!上图显示了操作符 [[和[的区别！---[返回结果依旧是一个list但是[[已经不是一个list了

》》具有list属性的类还有

1、call类对象：The first element of the call is the function that gets called. It’s usually the name of a function:

> x <- quote(read.csv("important.csv", row.names = FALSE))
> class(x)
[1] "call"
> lenth(x)

2、formula 类的对象

dat=data.frame(x1=rnorm(100,m=50),x2=rnorm(100,m=50),x3=rnorm(100,m=50),x4=rnorm(100,m=50),y=rnorm(100))
m2=lm(y~log(x1)+x2*x3,data=dat)
newFmla=formula(m2)

> class(newFmla)
[1] "formula"
> length(newFmla)
[1] 3
> newFmla[1]
`~`()
> newFmla[2]
y()
> newFmla[3]
(log(x1) + x2 * x3)()