Hi, everyone!

First-time poster, here, so please be forbearing if I've violated some of the conventions for asking questions (like, for example, providing a replicable example).

I'm trying to estimate a Generalized Additive Mixed Model using the "gamm" function with this code:

```
fit1.1 = gamm(opioidNonFatalOD ~ s(mandatoryReg.l2, k = 3, fx = TRUE,
bs = "cr") +
s(coalitionActive.l2, k = 3, fx = TRUE, bs = "cr") +
monthsSinceJan2011 +
everFunded +
ICD10 +
spoke5 +
hub +
s(monthly2, bs = "cc", fx = FALSE, k = 4) +
s(county2, bs = "re"),
#+ offset(log(population / 100000)),
correlation = corAR1(form = ~ monthsSinceJan2011 | county2),
data = tsData,
family = quasipoisson, offset = log(population / 100000),
niterPQL = 20,
verbosePQL = TRUE)type or paste code here
```

For some reason, it looks like the "offset" argument isn't getting passed to gammPQL. I get this error:

```
iteration 1
Quitting from lines 201-220 (pfs_model_experiments_041520.Rmd)
Error in lme(fixed = fixed, random = random, data = data, correlation = correlation, :
unused argument (offset = log(population/1e+05))
Calls: <Anonymous> ... withVisible -> eval -> eval -> gamm -> eval -> eval -> gammPQL
Execution halted
```

Here're the traceback messages:

```
Error in lme(fixed = fixed, random = random, data = data, correlation = correlation, : unused argument (offset = log(population/1e+05))
4.
gammPQL(y ~ X - 1, random = rand, data = strip.offset(mf), family = family, correlation = correlation, control = control, weights = weights, niter = niterPQL, verbose = verbosePQL, mustart = mustart, etastart = etastart, ...) at <text>#1
3.
eval(parse(text = paste("ret$lme<-gammPQL(", deparse(fixed.formula), ",random=rand,data=strip.offset(mf),family=family,", "correlation=correlation,control=control,", "weights=weights,niter=niterPQL,verbose=verbosePQL,mustart=mustart,etastart=etastart,...)", sep = "")))
2.
eval(parse(text = paste("ret$lme<-gammPQL(", deparse(fixed.formula), ",random=rand,data=strip.offset(mf),family=family,", "correlation=correlation,control=control,", "weights=weights,niter=niterPQL,verbose=verbosePQL,mustart=mustart,etastart=etastart,...)", sep = "")))
1.
gamm(opioidNonFatalOD ~ s(mandatoryReg.l2, k = 3, fx = TRUE, bs = "cr") + s(coalitionActive.l2, k = 3, fx = TRUE, bs = "cr") + monthsSinceJan2011 + everFunded + ICD10 + spoke5 + hub + s(monthly2, bs = "cc", fx = FALSE, k = 4) + s(county2, bs = "re"), ...
```

I've tried using the offset as a term in the model (see commented-out code), but get a similar error.

Just from inspecting the code, does anyone have an idea of what I'm doing wrong?

Thanks, David