codes {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

### 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.

### 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!

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