In R programming language I want to use a hash table.
在R编程语言中，我想使用哈希表。
How do I use the value of a variable as the key for the environment?
如何使用变量的值作为环境的关键？
For example:
例如：
map <- new.env(hash=T, parent=emptyenv())
key <- 'ddd'
map$key <- 4
print(ls(map))
>>[1] "key"
The output is 'key', which means I get a mapping from the string 'key' to the value 4. What I really want this code to do is to map the string 'ddd' to the value 4.
输出是'key'，这意味着我得到了从字符串'key'到值4的映射。我真正想要这个代码做的是将字符串'ddd'映射到值4。
How can I achieve this?
我怎样才能做到这一点？
PS. I don't use named list because it's slow with large amount of elements as it does not use hashing to do the search.
PS。我没有使用命名列表，因为它使用大量元素很慢，因为它不使用散列来进行搜索。
1 个解决方案
#1
26
As it says in ?"$":
正如它所说的那样？“$”：
Both ‘[[’ and ‘$’ select a single element of the list. The main
difference is that ‘$’ does not allow computed indices, whereas
‘[[’ does. ‘x$name’ is equivalent to ‘x[["name", exact =
FALSE]]’. Also, the partial matching behavior of ‘[[’ can be
controlled using the ‘exact’ argument.
So you want:
所以你要：
map[[key]] <- 4
> print(ls(map))
[1] "ddd" "key"
> map[[key]]
[1] 4
#1
26
As it says in ?"$":
正如它所说的那样？“$”：
Both ‘[[’ and ‘$’ select a single element of the list. The main
difference is that ‘$’ does not allow computed indices, whereas
‘[[’ does. ‘x$name’ is equivalent to ‘x[["name", exact =
FALSE]]’. Also, the partial matching behavior of ‘[[’ can be
controlled using the ‘exact’ argument.
So you want:
所以你要：
map[[key]] <- 4
> print(ls(map))
[1] "ddd" "key"
> map[[key]]
[1] 4