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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.
977
To get type of a value or variable or object in R programming, call typeof() function and pass the value/variable to it.
Object identity is a fundamental object orientation concept. With object identity, objects can contain or refer to other objects. Identity is a property of an object that distinguishes the object from all other objects in the application.
An identity in object-oriented programming, object-oriented design and object-oriented analysis describes the property of objects that distinguishes them from other objects.
Objects in java are characterized by three essential properties: state, identity, and behavior. The state of an object is a value from its data type. The identity of an object distinguishes one object from another. It is useful to think of an object's identity as the place where its value is stored in memory.
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.
179
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