如何通过遍历列创建字典/哈希表？ [英] How to create a dictionary / hash table by iterating through a column?

问题描述

我有一个两列的数据框：键和值，我想使用字典/哈希表的每个元素的每列的相应行来创建一个字典。

据了解，使用R字典/哈希表的典型方法是通过做类似的操作。

  labels.dic<  -  c（项目的ID和其他描述=id）
  

这样做的效果非常好，但是当我尝试使用数据框（在示例中名为 lbls ）中的值来执行它时，它不起作用。为什么会发生这种情况？

  labels.dic<  -  c（lbls [1,1] = lbls [1,2] ）
错误：c（lbls [1,1] =
  

解决方案

在我看来，你有一些错误的信息，我甚至不知道在哪里可以得到用于创建哈希表的语法。

在任何情况下：对于类似哈希表的功能，您可能需要考虑使用环境：这些工作内部使用散列表（如果我记得正确），所以做你想要的。

你会使用这样的东西：

  someenv< -new.env（）
 someenv [[key]]< -value 
  

鉴于您的 data.frame ，这样的东西将填补：

  for（i in seq（nrow（lbls）））
 {
 someenv [[lbls [i，1]]]<  -  lbls [i，2 ] 
} 
  

（注意：这要求第一列是一个实际的字符列，而不是一个因素!!）

然后可以使用 someenv [[nameofinterest ]] 。

I have a data frame of two columns: key and value and I would like to create a dictionary using the respective row of each column for each element of the dictionary / hash table.

As far as I understand the typical way of using R dictionaries / hash tables is by doing something similar to this.

labels.dic <- c("Id of the item and some other description" = "id")

This works perfectly fine but when I try to do it using the values from the data frame (named lbls in the example) it does not work. Why does this happen?

labels.dic <- c(lbls[1,1]=lbls[1,2])
Error: unexpected '=' in "c(lbls[1,1] ="

解决方案

It appears to me you've gotten some misinformation. I'm not even certain where you get the idea of that syntax for creating a hashtable.

In any case: for hashtable-like functionality, you may want to consider using an environment: these work internally with a hashtable (if I remember correctly), so do quite what you want to.

You would use this something like:

someenv<-new.env()
someenv[["key"]]<-value

Given your data.frame, something like this would fill it up:

for(i in seq(nrow(lbls)))
{
  someenv[[ lbls[i,1] ]]<- lbls[i,2]
}

(note: this requires that the first column is an actual character column, not a factor!!)

You can then easily get to a named value by using someenv[["nameofinterest"]].

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