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2002 Mar 12
0
Case weights in nlme models
...mericans, plus a case weighting variable. According to the survey's documentation, using the weight allows the oversampled study data to be representative of the 15,000-person random sample. All this is fine, and I've been able to run linear models on the data using lm() with the weights = WT2517 option (WT2517 is the column containing the weight variable). But the documentation for nlme() suggests that weights= takes something other than a straight vector: weights: an optional `varFunc' object or one-sided formula describing the within-group heteroscedasticity structure. If...