"eval" inside a function call in connection with updating the data slot in the call of lmer
On Sep 17, 2012, at 3:26 PM, S?ren H?jsgaard wrote:
Dear list, Given a linear mixed model (from lme4) I want to 1) first change the input dataset and then 2) change the model formula. I want this to happen in a function call; Please see below. Options 1) and 2) below work whereas 3) fails with the message
foo()
Error in is.data.frame(data) : object 'beets2' not found Question: What is it one must to in case 3) to have R look "inside" the function to figure out what "beets2" is?
That will depend on how you offer that 6 letter sequence to the interpreter. Surrounded by quotes will be quite different than without quotes
Best regards S?ren
________________
library(pbkrtest)
data(beets)
lgs <- lmer(sugpct~block+sow+harvest+(1|block:harvest), data=beets, REML=F)
foo <- function(){
## 1)
beets2 <- transform(beets, yy = sugpct * yield)
ma1 <- lmer(yy~block+sow+harvest+(1|block:harvest), data=beets2, REML=F)
ma0 <- update(ma1, yy~.)
## 2)
cl <- getCall(lgs)
cl[["data"]] <- beets2
mb1 <- eval(cl)
mb0 <- update(mb1, yy~.)
mb0
## 3)
cl <- getCall(lgs)
cl[["data"]] <- as.name("beets2")
The problem here is that 'beets2' is just a character vector ... with no binding.
I'm wondering if you instead want:
cl[["data"]] <- get("beets2")
mc1 <- eval(cl) mc0 <- update(mc1, yy~.) mc0 } foo()
No guarantees. I'm not a particularly experienced surgeon of lmer-objects.
David Winsemius, MD Alameda, CA, USA