ar mixed model. The user should be aware
that first, this preliminary analysis can take time for large datatsets and
second, that the generated initial values can be very not likely and even
may converge slowly to a local maximum.  This is the reason why several
alternatives exist. The vector of initial values can be directly specified
in <code>B</code> the initial values can be generated (automatically or randomly)
from a model with <code>ng=</code>. Finally, function <code>gridsearch</code> performs
an au