[R-sig-ME] [R] understanding I() in lmer formula

[Don Cohen]

Andrew Robinson writes:

 > can you provide a minimal executable example?
I was hoping it was going to be something simple.
It looks to me like this is related to parsing and has nothing
to do with the data.
I start by trying to simplify my formula and find that even deleting
seemingly irrelevant parts leads to the same kinds of errors.

 > > but what is that "~" doing in the error message??
I wish I knew!

Here's an example that's not exactly small, but at least smaller 
than I started with.  The first one seems to work and then I move
the # to the other line that I'd expect to have the same meaning.

> fullx=lmer(log.corti~ 
    z.n.fert.females*z.n.males+ 
    is.alpha2*(z.infanticide.susceptibility_new+z.min.co.res+z.co.res+z.log.tenure)+ 
    z.age.at.sample+sin.season+cos.season+ 
    (1+z.n.fert.females+z.n.males+is.alpha2.subordinate+z.infanticide.susceptibility_new+ 
     z.min.co.res+z.log.tenure+z.co.res+ 
     z.age.at.sample+sin.season+cos.season+ 
     I(z.n.fert.females*z.n.males)+ 
       I(is.alpha2.subordinate*z.co.res)+ 
      I(z.min.co.res*is.alpha2.subordinate)+ 
      #  I(is.alpha2.subordinate*z.min.co.res)+ 
     int.is.a.log.ten||monkeyid), 
        data=fe.re.xx$data, REML=F, control=contr)
+ + + + + + + + + + + + > fullx=lmer(log.corti~ 
    z.n.fert.females*z.n.males+ 
    is.alpha2*(z.infanticide.susceptibility_new+z.min.co.res+z.co.res+z.log.tenure)+ 
    z.age.at.sample+sin.season+cos.season+ 
    (1+z.n.fert.females+z.n.males+is.alpha2.subordinate+z.infanticide.susceptibility_new+ 
     z.min.co.res+z.log.tenure+z.co.res+ 
     z.age.at.sample+sin.season+cos.season+ 
     I(z.n.fert.females*z.n.males)+ 
       I(is.alpha2.subordinate*z.co.res)+ 
     # I(z.min.co.res*is.alpha2.subordinate)+ 
       I(is.alpha2.subordinate*z.min.co.res)+ 
     int.is.a.log.ten||monkeyid), 
        data=fe.re.xx$data, REML=F, control=contr) 
+ + + + + + + + + + + + Error in is.alpha2.subordinate * ~z.min.co.res :  
  non-numeric argument to binary operator 
>  

And if I start with the one that works and delete something
seemingly irrelevant, like z.infanticide.susceptibility_new+ 

> fullx=lmer(log.corti~ 
    z.n.fert.females*z.n.males+ 
    is.alpha2*(z.infanticide.susceptibility_new+z.min.co.res+z.co.res+z.log.tenure)+ 
    z.age.at.sample+sin.season+cos.season+ 
    (1+z.n.fert.females+z.n.males+is.alpha2.subordinate+ # z.infanticide.susceptibility_new+ 
     z.min.co.res+z.log.tenure+z.co.res+ 
     z.age.at.sample+sin.season+cos.season+ 
     I(z.n.fert.females*z.n.males)+ 
       I(is.alpha2.subordinate*z.co.res)+ 
      I(z.min.co.res*is.alpha2.subordinate)+ 
      #  I(is.alpha2.subordinate*z.min.co.res)+ 
     int.is.a.log.ten||monkeyid), 
        data=fe.re.xx$data, REML=F, control=contr) 
+ + + + + + + + + + + + Error in is.alpha2.subordinate * ~z.co.res :  
  non-numeric argument to binary operator 

I know this is not the minimal executable example requested, but I'm
hoping someone will have an idea before I try to simplify it further
and provide all you need to run it.