R help - Jun 2013 - load() into a data frame with my chosen name => .ThisEnv ?

very simple question.  I probably forgot the answer (early stage onset),
and I could not find it via google and r-help.

I have a number of files, each containing one saved data frame.  I want to
do the equivalent of

   d <- .GlobalEnv[[ load(file="dxxxx.Rdata") ]

but inside a function, and I don't need the original name (dxxxx).  in the
end, I want to do something like

   run <- function( i ) {
        fname <- paste0( "d", i, ".Rdata")
        stopifnot( length(fname)==1 )
        d <- .ThisEnv[[ load(file=fname) ]]
        coef( lm(d[,1] ~ d[,2]) )  ## calculate two coefficients and return
them
   }

   results <- mclapply( 1:10000, run )

stumped over something that should be easy...pointer appreciated.

/iaw
----
Ivo Welch (ivo.welch@gmail.com)

	[[alternative HTML version deleted]]

> very simple question.  I probably forgot the answer (early stage onset),
> and I could not find it via google and r-help.
> 
> I have a number of files, each containing one saved data frame.  I want to
> do the equivalent of
> 
>    d <- .GlobalEnv[[ load(file="dxxxx.Rdata") ]
Did you try using load's 'envir' argument, which should be mentioned
in its help file?
E.g., define the function
   getMyData <- function(RDataFile) {
       # RDataFile should be *.RData file containing exactly one object
       .ThisEnv <- new.env(parent = emptyenv())
       loadedNames <- load(file=RDataFile, envir=.ThisEnv)
       stopifnot(length(loadedNames)==1)
       .ThisEnv[[ loadedNames ]]
   }
and use it in the loop as
  d <- getMyData(RDataFile = fname)
   

Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com

> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at
r-project.org] On Behalf
> Of ivo welch
> Sent: Monday, June 17, 2013 4:08 PM
> To: r-help
> Subject: [R] load() into a data frame with my chosen name => .ThisEnv ?
> 
> very simple question.  I probably forgot the answer (early stage onset),
> and I could not find it via google and r-help.
> 
> I have a number of files, each containing one saved data frame.  I want to
> do the equivalent of
> 
>    d <- .GlobalEnv[[ load(file="dxxxx.Rdata") ]
> 
> but inside a function, and I don't need the original name (dxxxx).  in
the
> end, I want to do something like
> 
>    run <- function( i ) {
>         fname <- paste0( "d", i, ".Rdata")
>         stopifnot( length(fname)==1 )
>         d <- .ThisEnv[[ load(file=fname) ]]
>         coef( lm(d[,1] ~ d[,2]) )  ## calculate two coefficients and return
> them
>    }
> 
>    results <- mclapply( 1:10000, run )
> 
> stumped over something that should be easy...pointer appreciated.
> 
> /iaw
> ----
> Ivo Welch (ivo.welch at gmail.com)
> 
> 	[[alternative HTML version deleted]]
> 
> ______________________________________________
> 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.

For your problem, you might want to use saveRDS and readRDS instead of
save and load. I would also use dir to get a list of files rather
than paste. 

Then your solution might look like:


run <- function(filename) {
    df <- readRDS(filename);
    coef( lm(df[,1] ~ df[,2]) ) 
}

results <- lapply( dir(pattern=glob2rx('d*.rds')), run)

If this is disk-bound, using multiple threads probably won't help much.
You'll have to try it out for yourself.

-nfultz

On Mon, Jun 17, 2013 at 04:07:50PM -0700, ivo welch
wrote:
> very simple question.  I probably forgot the answer (early stage onset),
> and I could not find it via google and r-help.
> 
> I have a number of files, each containing one saved data frame.  I want to
> do the equivalent of
> 
>    d <- .GlobalEnv[[ load(file="dxxxx.Rdata") ]
> 
> but inside a function, and I don't need the original name (dxxxx).  in
the
> end, I want to do something like
> 
>    run <- function( i ) {
>         fname <- paste0( "d", i, ".Rdata")
>         stopifnot( length(fname)==1 )
>         d <- .ThisEnv[[ load(file=fname) ]]
>         coef( lm(d[,1] ~ d[,2]) )  ## calculate two coefficients and return
> them
>    }
> 
>    results <- mclapply( 1:10000, run )
> 
> stumped over something that should be easy...pointer appreciated.
> 
> /iaw
> ----
> Ivo Welch (ivo.welch at gmail.com)
> 
> 	[[alternative HTML version deleted]]
> 
> ______________________________________________
> 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.