form
a one sided formula of the form ~ t
, or ~ t |
g
, specifying a time covariate t
and, optionally, a
grouping factor g
. When a grouping factor is present in
form
, the correlation st
fixed
an optional logical value indicating whether the
coefficients should be allowed to vary in the optimization, or kept
fixed at their initial value. Defaults to FALSE
, in which case
the coefficients are allowed to vary.