relevel Reorder Levels of Factor

Description

The levels of a factor are re-ordered so that the level specified by ref is first and the others are moved down. This is useful for contr.treatment contrasts which take the first level as the reference.

Usage

relevel(x, ref, ...)

Arguments

x	an unordered factor.
ref	the reference level, typically a string.
...	additional arguments for future methods.

Details

This, as reorder(), is a special case of simply calling factor(x, levels = levels(x)[....]).

Value

A factor of the same length as x.

See Also

factor, contr.treatment, levels, reorder.

Examples

warpbreaks$tension <- relevel(warpbreaks$tension, ref = "M")
summary(lm(breaks ~ wool + tension, data = warpbreaks))