Hello,
The first argument to exists() must be the name of an object given as a
character string, as stated in the help page. See ?exists. You have also
forgot to initialize combined to NULL, this time.
Your function revised would then become
c_objects <- function(FILES) {
combined <- NULL
for (FILE in FILES) {
load(FILE)
if (exists("combined")) {
combined <- c(combined, res)
} else {
combined <- res
}
}
return(combined)
}
And all works as expected.
Hope this helps,
Rui Barradas
Em 18-06-2013 14:57, Davis, Brian escreveu:
In my haste to make a smaller example than my actual code I used 'is.null'
instead of 'exists' as is in my code. Here's a small reproducible example
res <- list(abc=letters, ABC=LETTERS)
save(res, file="results.RData")
res <- list(zyx=rev(letters), ZYX=rev(LETTERS))
save(res, file="results2.RData")
rm(res)
FILES <- c("results.RData", "results2.RData")
c_objects <- function(FILES) {
for (FILE in FILES) {
load(FILE)
if (exists(combined)) {
combined <- c(combined, res)
} else {
combined <- res
}
}
return(combined)
}
combined_results <- c_objects(FILES)
-----Original Message-----
From: Duncan Murdoch [mailto:murdoch.dun...@gmail.com]
Sent: Monday, June 17, 2013 5:40 PM
To: Davis, Brian
Cc: r-help@r-project.org
Subject: Re: [R] Help understanding environments
On 13-06-17 5:02 PM, Davis, Brian wrote:
I have a collection of .RData files that have result objects that I would like
to combine. Specifically, skatCohort objects from the skatMeta package, but
I've run into a similar issue with simple data.frames also.
If I run something like
FILES <- list.files(path="/path/to/my/results", pattern=".RData$",
full.names=TRUE) combined <- NULL
for (FILE in FILES) {
load(FILE)
if (!is.null(combined)) {
combined <- c(combined, res)
} else {
combined <- res
}
}
I get all my objects combined. However, if I wrap this into a
function I get the following error
c_objects <- function(FILES) {
combined <- NULL
for (FILE in FILES) {
load(FILE)
if (!is.null(combined)) {
combined <- c(combined, res)
} else {
combined <- res
}
}
return(combined)
}
combined_results <- c_objects(FILES)
Error in eval(expr, envir, enclos) : object 'combined' not found
How should I write this function such that it can find "combined". I've tried
reading the help on envirnaments, and the exisits function but I haven't been able to
figure this out. Are there any other resources to read up on this?
You are doing something that you aren't showing us: I don't see any calls to
eval(), but it's eval() that generated the error.
Calling traceback() after the error might be informative.
Duncan Murdoch
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