R help - Aug 2010 - How to remove all objects except a few specified objects?

How to remove all R objects in the RAM except for a few specified ones?
rm(list=ls()) removes all R objects in the R work space.

Another question is that whether removing all R objects actually releases
the RAM? Thanks.
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a <- 1
b <- 2
c <- 3

ls()[-a]  # set minus to all the objects you want to retain

rm(list = ls()[-a]  # will remove all the objects - except a

ls()  # presto
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If you are going to be doing this a lot, you may want to consider
making a little function.  Here is an example 'do not remove'
function.  It defaults to the global environment, but you can always
change it.  Also, if you try to keep a variable name that does not
exist, it will throw an error and not remove anything.  My assumption
is that when one of the names the user typed does not match a current
object, the user made a typo.

dnrm <- function(vars, envir = .GlobalEnv) {
  vars <- c(vars, "dnrm")
  keep <- match(x = vars, table = ls(envir = envir))
  if(any(is.na(keep))) {
    stop(paste("Some of the variables were not found in",
             environmentName(envir)))
  }
  rm(list = ls(envir = envir)[-keep], envir = envir)
  cat("Removed all but", length(keep), "objects from",
      environmentName(envir), fill = TRUE)
}

Cheers,

Josh

On Mon, Aug 23, 2010 at 12:00 PM, Cheng Peng <cpeng at usm.maine.edu>
wrote:
>
> How to remove all R objects in the RAM except for a few specified ones?
> rm(list=ls()) removes all R objects in the R work space.
>
> Another question is that whether removing all R objects actually releases
> the RAM? Thanks.
> --
> View this message in context:
http://r.789695.n4.nabble.com/How-to-remove-all-objects-except-a-few-specified-objects-tp2335651p2335651.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> R-help at r-project.org mailing list
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> PLEASE do read the posting guide
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> and provide commented, minimal, self-contained, reproducible code.
>


-- 
Joshua Wiley
Ph.D. Student, Health Psychology
University of California, Los Angeles
http://www.joshuawiley.com/

Hi Cheng,

Check out the keep() function in package:gdata.

And to be sure the "removed" objects are really removed from system 
memory i think you need to run gc().

hth,

Karl

On 8/23/2010 9:00 PM, Cheng Peng wrote:
>
> How to remove all R objects in the RAM except for a few specified ones?
> rm(list=ls()) removes all R objects in the R work space.
>
> Another question is that whether removing all R objects actually releases
> the RAM? Thanks.
-- 
Karl Brand <k.brand at erasmusmc.nl>
Department of Genetics
Erasmus MC
Dr Molewaterplein 50
3015 GE Rotterdam
P +31 (0)10 704 3409 | F +31 (0)10 704 4743 | M +31 (0)642 777 268

Thanks Josh and Karl. function dnrm() works well for my purpose. 
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If your specified objects have a certain pattern, you can use the 
parameter "pattern" in ls() to remove or keep it.
rm(list=ls(..., pattern="your_pattern"))
If not, possibly you have to manually specify them.

On 2010-8-24 3:00, Cheng Peng wrote:
> How to remove all R objects in the RAM except for a few specified ones?
> rm(list=ls()) removes all R objects in the R work space.
>
> Another question is that whether removing all R objects actually releases
> the RAM? Thanks.
>