Re quest: Documentation of formulae

I was at a loss to understand the use of "/" until I looked in "An
Introduction [!] to R," 
where I found the explanation.

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.