使用存储为字符串的名称以编程方式选择列表元素 [英] Select list element programmatically using name stored as string

问题描述

我有一个清单

myList = list(a = 1, b = 2)
names(myList)
# [1] "a" "b" 

我想通过存储在字符串中的名称从"myList"中选择元素.

I want to select element from 'myList' by name stored in as string.

for (name in names(myList)){
     print (myList$name)
}

这不起作用，因为名称="a"，"b".我的选择行实际上是说myList$"a"和myList$"b".我也尝试过:

This is not working because name = "a", "b". My selecting line actually saying myList$"a" and myList$"b". I also tried:

print(myList$get(name))
print(get(paste(myList$, name, sep = "")))

但是没有用.如果您能告诉我该怎么做，我非常感谢.

but didn't work. Thank you very much if you could tell me how to do it.

推荐答案

$进行完全匹配和部分匹配，myList$name等效于

$ does exact and partial match, myList$name is equivalent to

`$`(myList, name)

正如@Frank所指出的那样，第二个参数name将不被求值，但将被视为文字字符串.尝试?`$`并查看文档.

As @Frank pointed out, the second argument name won't be evaluated, but be treated as a literal character string. Try ?`$`and see the document.

在您的示例中. myList$name将尝试在myList

In your example. myList$name will try to look for name element in myList

这就是为什么您需要myList[[name]]

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