`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

`factor`

.levelsToKeep

An optional character vector giving the subset of

`levels(f)`

to be converted to dummy variables.`model.matrix`

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

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