In SAS and SPSS, selecting variables for an analysis is simple, while selecting observations is often much more complicated. In R, these two processes can be almost identical. As a result, variable selection in R is both more flexible and quite a bit more complex. However, since you need to learn that complexity to select observations, it does not require much added effort.
CITATION STYLE
Muenchen, R. A. (2011). Selecting Variables (pp. 161–186). https://doi.org/10.1007/978-1-4614-0685-3_7
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