[Rd] formula(CO2)

(Ted Harding) ted.harding at nessie.mcc.ac.uk
Mon Jul 16 15:57:56 CEST 2007

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:


  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,

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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