Re: [Rd] formula(CO2)

From: Gabor Grothendieck <ggrothendieck_at_gmail.com>
Date: Mon, 16 Jul 2007 10:42:19 -0400

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 ------------------------------
>



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