This is a side-effect of lapply being in the base namespace and not
evaluating its arguments, as explained on its help page which also points
out that using a wrapper is sometimes needed. It also points out that
code has been written that relies on the current behaviour.
On Mon, 8 Sep 2008, Tim Hesterberg wrote:
I've defined my own version of summary.default,
that gives a better summary for highly skewed vectors.
If I call
summary(x)
the method is used.
If I call
summary(data.frame(x))
the method is not used.
I've traced this to lapply; this uses the new method:
lapply(list(x), function(x) summary(x))
and this does not:
lapply(list(x), summary)
If I make a copy of lapply, WITHOUT the environment,
then the method is used.
lapply <- function (X, FUN, ...) {
FUN <- match.fun(FUN)
if (!is.vector(X) || is.object(X))
X <- as.list(X)
.Internal(lapply(X, FUN))
}
I'm curious to hear reactions to this.
There is a March 2006 thread
object size vs. file size
in which Duncan Murdoch wrote:
Functions in R consist of 3 parts: the formals, the body, and the
environment. You can't remove any part, but you can change it.
That is exactly what I want to do, remove the environment, so that
when I define a better version of some function that the better
version is used.
Here's a function to automate the process:
copyFunction <- function(Name){
# Copy a function, without its environment.
# Name should be quoted
# Return the copy
file <- tempfile()
on.exit(unlink(file))
dput(get(Name), file = file)
f <- source(file)$value
f
}
lapply <- copyFunction("lapply")
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Brian D. Ripley, [EMAIL PROTECTED]
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
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