update() inside a function only searches the global environment?

Question

I tried to write a wrapper function to do likelihood ratio tests in batches. I tried to include update() to update the initial model. However, it seems that instead of looki

Answer 1

I've been bitten by this behaviour before too, so I wrote my own version of update. It evaluates everything in the environment of the formula, so it should be fairly robust.

my_update <- function(mod, formula = NULL, data = NULL) {
  call <- getCall(mod)
  if (is.null(call)) {
    stop("Model object does not support updating (no call)", call. = FALSE)
  }
  term <- terms(mod)
  if (is.null(term)) {
    stop("Model object does not support updating (no terms)", call. = FALSE)
  }

  if (!is.null(data)) call$data <- data
  if (!is.null(formula)) call$formula <- update.formula(call$formula, formula)
  env <- attr(term, ".Environment")

  eval(call, env, parent.frame())
}

library(nlme4)

fake <- data.frame(
  subj = rep(1:5, 4), 
  factor1 = rep(LETTERS[c(1,2,1,2)], each = 5), 
  factor2 = rep(letters[1:2], each = 10), 
  data = sort(rlnorm(20)))

foo <- function() {
  temp <- fake
  model1 <- lmer(data ~ factor1 * factor2 + (1 | subj), fake)
  model1a <- my_update(model1, ~ . - factor1:factor2)
  model1a
}
foo()