Arguments
formula
a formula or a mvformula, the elements are not allowed
to be data.frames.
var.subset
optional vector of the variable numbers to use.
split.x
logical, whether explanatory terms that are matrices should be split and
each added as a single term. this is useful for plotting formulas.
intercept
numeric, either 1
if an Intercept should be included in the formula
or 0
if there shouldn't be an Intercept in the formula.
allow.noresp
logical, whether an empty response is allowed (a list with one element
would be returned) or not (would result in an error.)