attr                  package:base                  R Documentation

Object Attributes

Description:

     Get or set specific attributes of an object.

Usage:

     attr(x, which, exact = FALSE)
     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.

   exact: logical: should 'which' be matched exactly?

   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 (unless 'exact = TRUE') a
     unique partial match. (Setting
     'options(warnPartialMatchAttr=TRUE)' causes partial matches to
     give warnings.)

     The replacement function only uses exact matches.

     Note that some attributes (namely 'class', 'comment', 'dim',
     'dimnames', 'names', 'row.names' and 'tsp') are treated specially
     and have restrictions on the values which can be set. (Note that
     this is not true of 'levels' which should be set for factors via
     the 'levels' replacement function.)

     The extractor function allows (and does not match) empty and
     missing values of 'which': the replacement function does not.

Value:

     For the extractor, 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)

