lmeLevel object from its componentslmeLevel(precision, groups, columns, modelMatrix)pdMat object representing the relative
    precision matrix for the random effects.  This argument is missing
    in calls to generate the lmeLevel for the fixed-effects terms
    and for the response.lmeLevel for the fixed-effects terms
    and for the response.modelMatrix
    corresponding to this level of random or fixed effects.original slot of the
    containing reStruct objectlmeLevel object.lmeLevel object contains information on one level of
  random-effects terms or the fixed-effects terms or the response in a
  linear mixed-effects structure.lmeLevel-class, pdMat-class,
  reStruct-class