问题
is there a way to test whether two objects are identical in the R language?
For clarity: I do not mean identical in the sense of the identical function,
which compares objects based on certain properties like numerical values or logical values etc.
I am really interested in object identity, which for example could be tested using the is operator in the Python language.
回答1:
UPDATE: A more robust and faster implementation of address(x) (not using .Internal(inspect(x))) was added to data.table v1.8.9. From NEWS :
New function
address()returns the address in RAM of its argument. Sometimes useful in determining whether a value has been copied or not by R, programatically.
There's probably a neater way but this seems to work.
address = function(x) substring(capture.output(.Internal(inspect(x)))[1],2,17)
x = 1
y = 1
z = x
identical(x,y)
# [1] TRUE
identical(x,z)
# [1] TRUE
address(x)==address(y)
# [1] FALSE
address(x)==address(z)
# [1] TRUE
You could modify it to work on 32bit by changing 17 to 9.
回答2:
You can use the pryr package.
For example, return the memory location of the mtcars object:
pryr::address(mtcars)
Then, for variables a and b, you can check:
address(a) == address(b)
来源：https://stackoverflow.com/questions/10912729/r-object-identity