测试两个`data.table`是否指向相同的内存位置

Question

让我们:

DT1 <- data.table(iris)
DT2 <- DT1 # both reference the same memory location though
DT3 <- copy(DT1)

问题:有没有办法检查是否DT2继续引用相同的内存位置DT1？

像这样的伪函数:

mem.identical(DT2, DT1) # should return TRUE
mem.identical(DT3, DT1) # should return FALSE

---

不幸的是,identical或者all.equal不为此目的而工作,因为

identical(DT1,DT3) # gives TRUE

只有在引入一些变化后,才能使用identical以下方法检测差异:

DT1[,Test:=1] # introduces change to DT1 directly, to DT2 indirectly
identical(DT1,DT2) # TRUE - proves that DT2 is linked with DT1
identical(DT1,DT3) # FALSE - DT1 and DT3 are clearly decoupled

Answer 1

你可以用data.table::address它

> address(DT1)
[1] "0x10336c230"
> address(DT2)
[1] "0x10336c230"
> address(DT3)
[1] "0x10336cb50"