Abstract
In R, objects belong to classes as well as types and modes. Classes tell something about what the object contains. All objects belong to at least one class. The S3, S4, and Reference Class object systems differ regarding classes. In S3, there are specific classes into which an R object falls. In S4, the user defines a class for an S4 object. Classes in S3 are called informal classes, whereas classes in S4 are called formal classes. In both systems, classes are functional classes. In Reference Class, the classes are formal and referential. (For functional classes, an object is only changed when assigned a new value—locally. For referential classes, when an object changes, the value of the object changes everywhere the object is present.) Reference Class classes are usually defined for packages. This chapter covers the three kinds of classes.
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© 2022 The Author(s), under exclusive license to APress Media, LLC, part of Springer Nature
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Tollefson, M. (2022). Classes of Objects. In: R 4 Quick Syntax Reference. Apress, Berkeley, CA. https://doi.org/10.1007/978-1-4842-7924-3_5
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DOI: https://doi.org/10.1007/978-1-4842-7924-3_5
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Publisher Name: Apress, Berkeley, CA
Print ISBN: 978-1-4842-7923-6
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