Reorder Levels of Factor

Usage

relevel(x, ref, ...)

Arguments

x An unordered factor.
ref The reference level.
... Additional arguments for future methods.

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.

Value

A factor of the same length as x.

Author(s)

B.D. Ripley

See Also

factor, contr.treatment

Examples

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

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