$ 允许您从命名列表中按名称提取元素.例如

The $ allows you extract elements by name from a named list. For example

x <- list(a=1, b=2, c=3)
x$b
# [1] 2

您可以使用 names()

names(x)
# [1] "a" "b" "c"

这是一个基本的提取操作符.您可以在 R 中输入 ?Extract 来查看相应的帮助页面.

This is a basic extraction operator. You can view the corresponding help page by typing ?Extract in R.