understanding I() in lmer formula

If you don't get a prompt reply here, you might do better posting this
on the r-sig-mixed-models list (for obvious reasons).

Cheers,
Bert


Bert Gunter

"The trouble with having an open mind is that people keep coming along
and sticking things into it."
-- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )

 Is there a difference between I(x*y) and I(y*x) ?
I have a call to lmer that results in this complaint:
  Error in is.alpha2.subordinate * ~z.min.co.res :
  non-numeric argument to binary operator
when I change this line:
  I(is.alpha2.subordinate*z.min.co.res)+
to this:
  I(z.min.co.res*is.alpha2.subordinate)+
the complaint goes away.
I'd like to understand why.

______________________________________________
R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.

 Is there a difference between I(x*y) and I(y*x) ?
I have a call to lmer that results in this complaint:
  Error in is.alpha2.subordinate * ~z.min.co.res :

A reproducible example would help ...

In the absence of that, check the classes of the two variables in I() and, if you run the product on the command line, either inside I() or not, what's the class of the result?
If that is order-dependent for the object types you're combining, while I don't know why that might be it would go some way to explaining the outcome.

S Ellison



*******************************************************************
This email and any attachments are confidential. Any use...{{dropped:8}}

The suggestion to post on R-sig-ME was a good one.
The problem turned out to be a bug in lmer parsing, which is now fixed.

S Ellison writes:
 > >  Is there a difference between I(x*y) and I(y*x) ?
 > > I have a call to lmer that results in this complaint:
 > >   Error in is.alpha2.subordinate * ~z.min.co.res :
 > 
 > A reproducible example would help ...