relevel                 package:base                 R Documentation

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.

     ...: Additional arguments for future methods.

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))

