R help - Jun 2013 - Help understanding environments

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?

Thanks in advance,

-Brian

I probably should have been more specific.  The .RData objects which get loaded
have a list called 'res'.  This isn't a reproducible example, as I
haven't included any of the RData files.

-----Original Message-----
From: Rui Barradas [mailto:ruipbarradas at sapo.pt] 
Sent: Monday, June 17, 2013 4:25 PM
To: Davis, Brian
Subject: Re: [R] Help understanding environments

Hello,

The error I get is: Error: object 'res' not found You are using an
undefined variable, 'res'. I don't believe this has something to do
with environments.

Rui Barradas


Em 17-06-2013 22:02, Davis, Brian escreveu:
> 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?
>
> Thanks in advance,
>
> -Brian
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide 
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

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