Hi readers,

I'm new to the R package and have a question about handling missing data in
R.  I have a dataset from a longitudinal study where we are are testing a
series of models, some in which lagged variables are used to predict an
outcome and others in which concurrent variables are used.  Due to the
nature of our experiment, every participant (or case) has missing data for
the first observation for all of the lagged variables.

My question is how does R handle missing data of this nature.  My concern is
that if I use listwise deletion, I would end up deleting all the
participants in the dataset.  However, I don't want to omit the first
observation from analysis either.  Is it possible to simply omit the first
observation when the lagged variables are in the model (that is, when there
is missing data from the first observation), but include the first
observation when there are not lagged variables in the model (that is, when
there is no missing data)?

Thanks,

Tim

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