Re: [Rd] formula(CO2)

From: Ted Harding <ted.harding_at_nessie.mcc.ac.uk>
Date: Mon, 16 Jul 2007 14:57:56 +0100 (BST)


On 16-Jul-07 13:28:50, Gabor Grothendieck wrote:
> The formula attribute of the builtin CO2 dataset seems a bit strange:
>

>> formula(CO2)

> Plant ~ Type + Treatment + conc + uptake
>
> What is one supposed to do with that? Certainly its not suitable
> for input to lm and none of the examples in ?CO2 use the above.

I think one is supposed to ignore it! (Or maybe be inspired to write a mail to the list ... ).

I couldn't find anything that looked like the above formula from str(CO2). But I did spot that the order of terms in the formula: Plant, Type, treatment, conc, uptake, is the same as the order of the "columns" in the dataframe.

So I tried:

  D<-data.frame(x=(1:10),y=(1:10))

  formula(D)
  x ~ y

So, lo and behold, D has a formula!

Or does it? Maybe if you give formula() a dataframe, it simply constructs one from the "columns".

Best wishes,
Ted.



E-Mail: (Ted Harding) <Ted.Harding_at_manchester.ac.uk> Fax-to-email: +44 (0)870 094 0861
Date: 16-Jul-07                                       Time: 14:57:28
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