How to use lmer inside a function - r

Question

I'm trying to write a function that collects some calls I use often in scripts
I use the sleepstudy data of the lme4 package in my examples
Here's (a simplified version of) the function I started with:
trimModel1 <- function(frm, df) {
require(LMERConvenienceFunctions)
require(lme4)
lm<-lmer(frm,data=df)
lm.trimmed = romr.fnc(lm, df)
df = lm.trimmed$data
# update initial model on trimmed data
lm<-lmer(frm,data=df)
# lm#call$formula<-frm
mcp.fnc(lm)
lm
}
When I call this function like below:
(fm1<-trimModel1(Reaction ~ Days + (Days|Subject),sleepstudy))
The first three lines of the output look like this:
Linear mixed model fit by REML
Formula: frm
Data: df
If I had called the commands of the trimModel1 function in the console the first three lines of the summary of the model look like this:
Linear mixed model fit by REML
Formula: Reaction ~ Days + (Days | Subject)
Data: sleepstudy
The difference is a problem because several packages that use the lme4 package make use of the formula and data fields. For instance the effects package uses these fields and a command like below will not work when I use the trimModel1 function above:
library(effects)
plot(allEffects(fm1))
I looked around on stackoverflow and R discussion groups for a solution and saw that you could change the formula field of the model. If you uncomment the lm#call$formula<-frm line in the trimModel1 function the formula field in the summary is displayed correctly. Unfortunately when I run a function from the effects package now I still get the error:
Error in terms.formula(formula, data = data) :
'data' argument is of the wrong type
This is because the data field is still incorrect.
Another possible solution I found is this function:
trimModel2 <- function(frm, df) {
require(LMERConvenienceFunctions)
require(lme4)
lm<-do.call("lmer",list(frm,data=df))
lm.trimmed = romr.fnc(lm, df)
df = lm.trimmed$data
# update initial model on trimmed data
lm<-do.call("lmer",list(frm,data=df))
mcp.fnc(lm)
lm
}
When I now type the following commands in the console I get no errors:
(fm2<-trimModel2(Reaction ~ Days + (Days|Subject),sleepstudy))
plot(allEffects(fm2))
The allEffects function works but now the problem is that the the summary of the fm2 model displays the raw sleepstudy data. That is not a big problem with the sleepstudy data but with very large datasets sometimes Rstudio crashed when displaying a model.
Does anyone know how to make one (or both) of these functions work correctly?
I think I have to change the fm1#call$data field but I don't know how.

Answer 1

Do it like this:
trimModel1 <- function(frm, df) {
require(LMERConvenienceFunctions)
require(lme4)
dfname <- as.name(deparse(substitute(df)))
lm<-lmer(frm,data=df)
lm.trimmed = romr.fnc(lm, df)
df = lm.trimmed$data
# update initial model on trimmed data
lm<-lmer(frm,data=df)
lm#call$formula <- frm
lm#call$data <- dfname
mcp.fnc(lm)
lm
}
It's the "deparse-substitute trick" to get an object name from the object itself.