From ggrothendieck at gmail.com  Mon Jul 16 16:42:19 2007
From: ggrothendieck at gmail.com (Gabor Grothendieck)
Date: Mon, 16 Jul 2007 10:42:19 -0400
Subject: [Rd] formula(CO2)
In-Reply-To: <XFMail.070716154040.ted.harding@nessie.mcc.ac.uk>
References: <971536df0707160716i7084039cp48560beb367fa141@mail.gmail.com>
	<XFMail.070716154040.ted.harding@nessie.mcc.ac.uk>
Message-ID: <971536df0707160742n1507968dwbaa1ef315c0f57e@mail.gmail.com>

Note that the formula uptake ~. will do the same thing so its not clear
how useful this facility really is.

On 7/16/07, Ted Harding <ted.harding at nessie.mcc.ac.uk> wrote:
> On 16-Jul-07 14:16:10, Gabor Grothendieck wrote:
> > Following up on your comments it seems formula.data.frame just creates
> > a formula whose lhs is the first column name and whose rhs is made up
> > of the remaining column names.  It ignores the "formula" attribute.
> >
> > In fact, CO2 does have a formula attribute but its not extracted by
> > formula.data.frame:
> >
> >> CO2 at formula
> > uptake ~ conc | Plant
> >> formula(CO2)
> > Plant ~ Type + Treatment + conc + uptake
>
> Indeed! And, following up yet again on my own follow-up comment:
>
> library(combinat)
>
> for(j in (1:4)){
>  for(i in combn((1:4),j,simplify=FALSE)){
>    print(formula(CO2[,c(5,i)]))
>  }
> }
> uptake ~ Plant
> uptake ~ Type
> uptake ~ Treatment
> uptake ~ conc
> uptake ~ Plant + Type
> uptake ~ Plant + Treatment
> uptake ~ Plant + conc
> uptake ~ Type + Treatment
> uptake ~ Type + conc
> uptake ~ Treatment + conc
> uptake ~ Plant + Type + Treatment
> uptake ~ Plant + Type + conc
> uptake ~ Plant + Treatment + conc
> uptake ~ Type + Treatment + conc
> uptake ~ Plant + Type + Treatment + conc
>
> opening the door to automated fitting of all possible models
> (without interactions)!
>
> Now if only I could find out how to do the interactions as well,
> I would never need to think again!
>
> best wishes,
> Ted.
>
> --------------------------------------------------------------------
> E-Mail: (Ted Harding) <ted.harding at nessie.mcc.ac.uk>
> Fax-to-email: +44 (0)870 094 0861
> Date: 16-Jul-07                                       Time: 15:40:36
> ------------------------------ XFMail ------------------------------
>



[Rd] formula(CO2)
Gabor Grothendieck