attr
Attribute of an Object

### Description

Returns a specific attribute of an object. Attributes specify the characteristics of any data object. This function can also be used to create a new attribute.

### Usage

    attr(x, which, exact = FALSE)
    attr(x, which) <- value

### Arguments

x | any object
which | a character string specifying an attribute of x.
exact | a logical value. If FALSE, which can be a partial attribute name. The default is FALSE.
value | an object or expression.

### Details

attr can be used to set and get user-defined attributes.
To explicitly delete the which attribute of x, use attr(x, which) <- NULL.
When you make an assignment, remember that the following attributes accept only certain valid values. See their individual topics for more information:

- names
- dim
- dimnames
- class
- comment
- row.names
- tsp

The semantics of attr are defined by saying that attr(x, which) is equivalent to attributes(x)[[which]] for either extracting or replacing attributes, with the restriction that which is interpreted as mode character. The value of attributes(x) is a list object (possibly of length 0) associated implicitly with any object x.
See Subscript for the semantics of [[.
Value

attr(x, which) | returns the which attribute of x, if it exists; otherwise, it returns NULL.
attr(x, which) <- value | returns value.

Side Effects
The assignment version of this function changes an attribute of x.
Adding or removing the "dim" attribute typically affects the class of x. In some cases, attributes affect other attributes. For example, assigning dim to a vector, a matrix, or an array removes the names and dimnames attributes. See dim for more information.
See Also
attributes, length, mode, structure, Subscript, class, dim, dimnames, levels, names, tsp
Examples

    attr(Sdatasets::gas, "dimnames")   # equivalent to dimnames(gas)
    # Set and remove custom attributes
    x <- c(a=7, b=11)
    a <- list(one=13, two='foo')
    attr(x, "myAttribute") <- a
    identical(attr(x, "myAttribute"), a)
    identical(attr(x, "my"), a)  # partial matching
    attr(x, "my", exact=TRUE)  # exact matching, returns NULL
    attr(x, "myAttribute") <- NULL

Package base version 6.1.5-18
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