From mark_difford at yahoo.co.uk  Fri May 30 23:11:59 2008
From: mark_difford at yahoo.co.uk (Mark Difford)
Date: Fri, 30 May 2008 14:11:59 -0700 (PDT)
Subject: [Rd] Re quest: Documentation of formulae
In-Reply-To: <o5n044t0444q8a0ne9ci4a8gv6kqknhrqg@4ax.com>
References: <o5n044t0444q8a0ne9ci4a8gv6kqknhrqg@4ax.com>
Message-ID: <17568035.post@talk.nabble.com>


Hi Mike,

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

I am not with you on the [!], because the information is basically where you
are "complaining" that it isn't, viz in your face --- i.e. in the
introductory document ---, but the operator surely deserves a mention in
?formula.  So on that score I agree with you.

Best, Mark.


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.
> 
> ______________________________________________
> R-devel at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel
> 
> 

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[Rd] Re quest: Documentation of formulae
Mark Difford