codes                  package:base                  R Documentation

Factor Codes

Description:

     This (generic) function returns a numeric coding of a factor.  It
     can also be used to assign to a factor using the coded form.

Usage:

     codes(x, ...)
     codes(x) <- value

Arguments:

       x: an object from which to extract or set the codes.

     ...: further arguments passed to or from other methods.

Value:

     For an ordered factor, it returns the internal coding (1 for the
     lowest group, 2 for the second lowest, etc.).

     For an unordered factor, an alphabetical ordering of the levels is
     assumed, i.e., the level that is coded 1 is the one whose name is
     sorted first according to the prevailing collating sequence.
     Warning: the sort order may well depend on the locale, and should
     not be assumed to be ASCII.

Note:

     Normally `codes' is not the appropriate function to use with an
     unordered factor.  Use `unclass' or `as.numeric' to extract the
     codes used in the internal representation of the factor, as these
     do not assume that the codes are sorted.

     The behaviour for unordered factors is dubious, but compatible
     with S version 3.  To get the internal coding of a factor, use
     `as.integer'.  Note in particular that the codes may not be the
     same in different language locales because of collating
     differences.

See Also:

     `factor', `levels', `nlevels'.

Examples:

     codes(rep(factor(c(20,10)),3))

     x <- gl(3,5)
     codes(x)[3] <- 2
     x

     data(esoph)
     ( ag <- esoph$alcgp[12:1] )
     codes(ag)

     codes(factor(1:10)) # BEWARE!

