CODEWITHSUNDEEP
rclassattr
Qaswed
Qaswed

Reputation: 3879

Why using `attr(x, "class")` instead of `class(x)`?

The function model.frame.default runs the following code; is.null(attr(data, "class")). My question is, why using attr in this case? Wouldn't it be more straight forward to use is.null(class(data))? (And doesn't it contradict to what is said here: Why is names(x) better than attr(x, "names")?)

Upvotes: 0

Views: 47

Answers (1)

Roland
Roland

Reputation: 132949

These are not equivalent. Compare the output of class(1) with attr(1, "class"). The latter returns only explicit S3 classes, the former also implicit classes.

Upvotes: 2

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