This isn't particularly helpful because the book is quite old but formula notation/functionality is covered in depth in "Statistical Models in S" by Chambers and Hastie. My guess is that there is strong consistency between what is said in there and how things work in R.
On Fri, May 30, 2008 at 4:19 PM, Mike Prager wrote:
In working through material on p.272 of MASS (4th ed.), I came across the following model formula: pet1.lm <- lm(Y ~ No/EP - 1, Petrol) I was at a loss to understand the use of "/" until I looked in "An Introduction [!] to R," where I found the explanation. My request is that more complete material on model formulae be lifted from "Introduction to R" (or elsewhere) and put into the main online help files. There are other useful notations that may not be well known. Since formulae are not limited to any particular function, perhaps an entry could be made under "Formula". More justification: The help for "lm" does not explain this notation, nor did I find a cross-reference to anything useful there. The R Reference Manual seems to explain functions only. The R Language Definition has no index entry for "formula" or "model formulae". Looking to print, neither the section on "model formula" on p.56 of MASS nor the section surrounding the above example explains the notation, nor could I find it in Dalgaard's book, nor in Maindonald and Braun. This seems too nice a feature to keep hidden in plain sight. -- Mike Prager, NOAA, Beaufort, NC * Opinions expressed are personal and not represented otherwise. * Any use of tradenames does not constitute a NOAA endorsement.
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