design.digest
.
addcp(x, n.cp, cp.values, cp.place)
design.digest
for a description of the arguments.
fac.design
object, with center points added as requested. A "hidden"
(i.e. non-printing) factor
Quad
is added to the design if there are
center points, that is used
by
fac.aov
to fit a quadratic term to the center points.
The contrasts of the returned
fac.design
are specified in the returned
design. They are set so that the center points are used to estimate a
quadratic effect of center points versus design points, via the "dummy"
factor
Quad
. In addition, the contrasts are set so that every
estimated terms in the model fit by the default
formula(x)
has equal
standard error.