attr                  package:base                  R Documentation

Object Attributes

Description:

     Get or set specific attributes of an object.

Usage:

     attr(x, which)
     attr(x, which) <- value

Arguments:

       x: an object whose attributes are to be accessed.

   which: a non-empty character string specifying which attribute is to
          be accessed.

   value: an object, the new value of the attribute, or 'NULL' to
          remove the attribute.

Details:

     These functions provide access to a single attribute of an object.
     The replacement form causes the named attribute to take the value
     specified (or create a new attribute with the value given).

     The extraction function first looks for an exact match to 'which'
     amongst the attributes of 'x', then a unique partial match.  The
     replacement function only uses exact matches.

     Note that some attributes (namely 'class', 'comment', 'dim',
     'dimnames', 'names', (from R 2.4.0) 'row.names' and 'tsp') are
     treated specially and have restrictions on the values which can be
     set.

     Specifying 'which' as a character 'NA' is interpreted as '"NA"'
     and not as a missing value.

Value:

     For the first form, the value of the attribute matched, or 'NULL'
     if no exact match is found and no or more than one partial match
     is found.

References:

     Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) _The New S
     Language_. Wadsworth & Brooks/Cole.

See Also:

     'attributes'

Examples:

     # create a 2 by 5 matrix
     x <- 1:10
     attr(x,"dim") <- c(2, 5)

