[R] model non-nested random effects in nlme library

[mwege]

Hello all,

In lme4 if you want to model two non-nested random effects you code it like
this:

mod1 <- lmer(y~x + (1|randomvar1) + (1|randomvar2))

How would you go about to model something similar in nlme?

In my database I have two variables for which I have repeated measures, lets
call them "individual" and "year".
But none of the "individuals" were measured in more than one year. So as I
understand it, I should not nest individual in year or visa versa.
 Someone suggested I do it as above. But I am accustomed to nlme, and dont
know how one would code non-nested random effects.

In the Pinheiro and Bates book there is an example coded like this:
modB <- lme(y~x,
  +   random = pdBlocked(list(pdIdent(~year-1), pdIdent(~individual-1))))

But when I try it I keep getting an error message saying:  "Error in
getGroups.data.frame(dataMix, groups) : 
  Invalid formula for groups"

What am I doing wrong?

Thank you,

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