将data.table转换为数据帧而不进行复制 [英] Convert a data.table to a data frame without copying

问题描述

此问答题集询问如何将data.frame转换为data.table而不复制，并演示如何使用手动方法和优秀的 setDT（）函数。

如何安全地将从 数据表转换回数据框架而不复制？

解决方案

我认为这是一个完全错误的想法，列出所有原因在上面的注释，可能是我不知道，但你可以替换 [。data.table 函数与 [data.frame 。这将防止@Arun提出的关于需要为 [ - functions：

  assignInNamespace（[.data.table，getAnywhere（`[.data.frame`），ns =data.table）
  / pre> 
 
 
通常检查'data.frame'类的所有函数都会因为继承而正常工作。
 
 
 
编辑：Arun的注释提供了一个不太剧烈的方法，因为覆盖核心data.table'[' - 功能本质上是不诚实。我想一个更诚实的方法是unnoad整个NAMESPACE。如果目标是使用 fread ，我想知道是否可以导入该函数和任何依赖。
  setattr（DT，'class'，'data.frame'）
  
 
 $ b b 
但仍然认为这是倒退。
 
This question and answer set asks how to convert a data.frame to a data.table without copying and shows how to do so using a manual method and the excellent setDT() function.

How would one safely convert back from a data.table to a data frame without copying? The issues and reasoning are similar to the question linked above.
解决方案
I think this is an entirely misguided idea for all the reasons listed in the comments above, and probably ones that I am not aware of, but you can replace the [.data.table function with [data.frame. That would prevent the problem raised by @Arun regarding needing to use an extra argument for the [-function:
 assignInNamespace( "[.data.table", getAnywhere( `[.data.frame`), ns="data.table") 
All of the functions which would normally check for 'data.frame'-class would already have worked normally because of inheritance.

Edit: The comment by Arun provides a much less drastic approach, since over-writing the core data.table '['-function is essentially "dishonest". I suppose a more honest approach would be to unLoad the entire NAMESPACE. If the goal is to just use fread, I wonder if there could just be importation of that functions and any dependencies.
 setattr(DT, 'class', 'data.frame')
But still see this as a "step backward."

                        
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