Produce a design matrix from a `mars' object.
# S3 method for mars model.matrix(object, x, which, full = FALSE, …)
a mars object.
optional argument; if supplied, the mars basis functions are evaluated at these new observations.
which columns should be used. The default is to use the
columns described by the component
TRUE the entire set of columns are selected,
even redundant ones. This is used for updating a mars fit.
further arguments to be passed from or to methods.
A model matrix corresponding to the selected columns.