[R-sig-ME] Problem with bootMer and models with offset

[Martin Hecht]

Hi,

I am using the latest version of R (3.1.1) and lme4 (1.1-7) .

I'm getting some weird implausible bootstrap results from bootMer for a
model with an offset (models without offset work fine).

I've attached an Rdata file with the returned object from lmer (lmerObj)
and the returned object from bootMer (booted)

Any help would be appreciated very much.


the syntax is:

booted <- bootMer ( x = lmerObj , FUN =
function(fit){return(c(fixef(fit),getME(fit,'theta')))} , nsim = 100 ,
seed = 65835 , verbose = TRUE )

> booted$t0[1]
(Intercept)
    2.606621

> mean(booted$t[,1])
[1] -78.21035

> boot::boot.ci ( booted , conf = 0.95 , type = "basic" , index = 1 )
BOOTSTRAP CONFIDENCE INTERVAL CALCULATIONS
Based on 100 bootstrap replicates

CALL :
boot::boot.ci(boot.out = booted, conf = 0.95, type = "basic",
    index = 1)

Intervals :
Level      Basic        
95%   (69.864, 95.425 ) 
Calculations and Intervals on Original Scale
Some basic intervals may be unstable