[R] Using functions within functions (environment problems)

[Gabor Grothendieck]

Check out this post and the entire thread to which it belongs:

http://finzi.psych.upenn.edu/R/Rhelp02a/archive/67474.html

On 1/26/07, Colin Beale <c.beale at macaulay.ac.uk> wrote:
> Hi everyone,
>
> I've been having difficulty writing wrapper functions for some
> functions where those same functions include other functions with
> eval()
> calls where the environment is specified. A very simple example using
> function lmer from lme4:
>
> lmerWrapper <- function(formula, data, family = gaussian, method =
> c("REML",
>    "ML", "PQL", "Laplace", "AGQ"), control = list(), start = NULL,
>    subset, weights, na.action, offset, contrasts = NULL, model =
> TRUE,
>
>    ...)
> {
>
>    xNew <- runif(0,1, length(data[,1]))
>    fNew <- sample(1:4, length(data[,1]), replace = T)
>    data <- as.data.frame(cbind(data, xNew, fNew))
>    formula <- update(formula, .~. + xNew + (1|fNew))
>    out <- lmer (formula = formula, data = data, family = family,
> method =
>        method, weights = weights, control = control, start = start,
>        subset = subset, na.action = na.action, offset = offset,
>        contrasts = contrasts, model = model)
> }
>
> dat <- data.frame(Y = rnorm(100), X1 = rnorm(100), X2 = rnorm(100),
>        F1 = as.factor(sample(1:4, 400, replace = T)))
> test <- lmerWrapper (Y ~ X1 + X2 + (1|F1), data = dat)
>
>
> This function attempts to create two new variables, add these to the
> data.frame and modify the formula for include these two new variables,
> and then fit this expanded model using lmer. Clearly the example is
> silly, but it illustrates the problem as it fails with the error:
>
> Error in eval(expr, envir, enclos) : object "xNew" not found
>
> because a function within lmer (lmerFrames) makes an eval call where
> the environment is specified as the .GlobalEnv which doesn't contain
> xNew - it needs to be looking in the environment from which it was
> called rather than going right back to the root. In a more general
> context, I might like to create a function where I don't specify a new
> data.frame in the wrapper, but want the function to search the back
> down
> the search path for each component, finding xNew in the environment of
> the wrapper function and X1 in the .GlobalEnv. Is there a general
> solution to this? Or do I need to create a modified lmer function that
> calls a modified lmerFrames function where I specify the environment
> differently? There's quite a lot in the archives dealing with
> environments and search paths, but I'm either not understanding how to
> apply the wisdom therein, or not finding the specific answer to my
> problem, and I should say that I have this problem with more than just
> the lmer function.
>
> Thanks for any pointers,
>
> Colin
>
> > sessionInfo()
> R version 2.4.1 (2006-12-18)
> i386-pc-mingw32
>
> locale:
> LC_COLLATE=English_United Kingdom.1252;LC_CTYPE=English_United
> Kingdom.1252;LC_MONETARY=English_United
> Kingdom.1252;LC_NUMERIC=C;LC_TIME=English_United Kingdom.1252
>
> attached base packages:
> [1] "stats"     "graphics"  "grDevices" "datasets"  "tcltk"
> "utils"
>    "methods"   "base"
>
> other attached packages:
>      debug    mvbutils        lme4      Matrix     lattice
> svSocket
>       svIO      R2HTML      svMisc       svIDE
>    "1.1.0"     "1.1.1" "0.9975-10"  "0.9975-8"   "0.14-16"
> "0.9-5"
>    "0.9-5"      "1.58"     "0.9-5"     "0.9-5"
>
>
>
>
> Dr. Colin Beale
> Spatial Ecologist
> The Macaulay Institute
> Craigiebuckler
> Aberdeen
> AB15 8QH
> UK
>
> Tel: 01224 498245 ext. 2427
> Fax: 01224 311556
> Email: c.beale at macaulay.ac.uk
>
>
>
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