dummy {lme4}  R Documentation 
Largely a wrapper for model.matrix
that
accepts a factor, f
, and returns a dummy
matrix with nlevels(f)1
columns (the first
column is dropped by default). Useful whenever one wishes to avoid
the behaviour of model.matrix
of always returning
an nlevels(f)
column matrix, either by the
addition of an intercept column, or by keeping one
column for all levels.
dummy(f, levelsToKeep)
f 
An object coercible to 
levelsToKeep 
An optional character vector giving the subset of

A model.matrix
with dummy variables as columns.
data(Orthodont,package="nlme")
lmer(distance ~ age + (ageSubject) +
(0+dummy(Sex, "Female")Subject), data = Orthodont)