Re: [Rd] formula(CO2)

From: Ted Harding <ted.harding_at_nessie.mcc.ac.uk>
Date: Mon, 16 Jul 2007 15:40:40 +0100 (BST)


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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