The outcome variable in my dataset is cost. I prefer not to transform it as readers will really be interested in pounds, not log(pounds) or sqrt(pounds). I have fitted my model using lme and now wish to use boot on it. I have therefore plagiarised the example in the article in RNews 2/3 December 2002
after loading the dataset I source this file ==================================================== require(boot) require(nlme) model.0 <- lme(tot ~ time + timepost + pct + totpat + (time + timepost) : single + single + (time + timepost) : train + train + time:gpattend + timepost:gpattend + gpattend, data = common, random = ~time + timepost | gp ) ints.9 <- intervals(model.0, which="fixed")$fixed[9,] # common$fit <- fitted(model.0) common$res <- resid(model.0, type = "response") cats.fit <- function(data) { mod <- lme(tot ~ time + timepost + pct + totpat + (time + timepost) : single + single + (time + timepost) : train + train + time:gpattend + timepost:gpattend + gpattend, data = data, random = ~ time + timepost | gp) summ <- summary(mod) c(fixef(summ), diag(summ$varFix)) } model.fun <- function(d, i) { d$tot <- d$fit+d$res[i] cats.fit(d) } tot.boot <- boot(common, model.fun, R=999) ============================================ So I fit the model and then generate fitted values and residuals which I use within the model.fun function to generate the bootstrap resample. If I do this the plot looks fine as does the jack.after.boot plot but the confidence intervals are about 10% of the width of the ones from the lme output. I wondered whether I was using the wrong fitted and residuals so I added level = 0 to the calls of fitted and resid respectively (level = 1 is the default) but this seems to lead to resamples to which lme cannot fit the model. Can anyone spot what I am doing wrong? I would appreciate a cc'ed response as my ISP has taken to bouncing the digest posts from R-help with probability approximately 0.3. FWIW I am using 2.1.0 under XP (SP2) with the versions of boot and nlme which shipped with the binary. Michael Dewey [EMAIL PROTECTED] http://www.aghmed.fsnet.co.uk/home.html ______________________________________________ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html