通过变量引用列表元素名称

Question

请问有没有办法通过变量引用列表元素名:

Labels <- vector(mode = "list") # Make a list called "Labels"
Labels[[1]] <- c(1,3,5,7) # Assign value to the first list element
names(Labels)[1] <- "Name" # Assign the name "Name" to the first list element
print(Labels)
print(Labels$Name)
# [1] 1 3 5 7

# Now I have the name of the first list element "Name"
# in the variable "ElementName"
ElementName <- "Name"

# How R will understand in the next line
# that I refer to the value "Name" of the variable "ElementName"
# in order to get 
# [1] 1 3 5 7

print(Labels$ElementName)

Answer 1

我们可以使用 [[ 来提取 list 元素。

Labels[[ElementName]]
#[1] 1 3 5 7

如果我们使用 list 元素的名称，我们使用引号

Labels[['Name']]
#[1] 1 3 5 7

有关详细信息，请查看 ?"[[" 或 ?Extract