Robert Gentleman
Modeling with Objects
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The 1991 revision of the S language introduced several new concepts. In this
paper we show how three of these: dataframes, formulas, and object oriented
programming can be used to simplify the manipulation of complex data.
We consider the case where the data contain a longitudinal component and show
how using an appropriate data structure provides an abstraction that allows
these data to be handled and modeled in a very natural way.
The ideas extend to other situations where components of the data collected have
complex structure.