From ted.harding at nessie.mcc.ac.uk  Mon Jul 16 17:13:18 2007
From: ted.harding at nessie.mcc.ac.uk ( (Ted Harding))
Date: Mon, 16 Jul 2007 16:13:18 +0100 (BST)
Subject: [Rd] formula(CO2)
In-Reply-To: <971536df0707160742n1507968dwbaa1ef315c0f57e@mail.gmail.com>
Message-ID: <XFMail.070716161318.ted.harding@nessie.mcc.ac.uk>

On 16-Jul-07 14:42:19, Gabor Grothendieck wrote:
> Note that the formula uptake ~. will do the same thing so its
> not clear how useful this facility really is.

Hmmm... Do you mean somthing like

  lm(uptake ~ . , data=CO2[,i])

where i is a subset of (1:4) as in my code below? In which case
I agree!

Ted.


> 
> 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
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>>
> 
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E-Mail: (Ted Harding) <ted.harding at nessie.mcc.ac.uk>
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Date: 16-Jul-07                                       Time: 16:13:15
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[Rd] formula(CO2)
 (Ted Harding