R help - Oct 2012 - append for .Rdata?

Can i somehow append objects to an .Rdata file?

I didn't see an option for it in the save() method. 

dump() won't work since i have s4 objects in there.

On 09/10/2012 16:35, Jessica Streicher wrote:
> Can i somehow append objects to an .Rdata file?
No.  See the 'R Internals' manual for the details.

BTW, it is '.RData': R is case sensitive and so are many file systems.

It sounds like you should be using a database of the results of 
saveRDS() for each object (which is what lazy-loading uses, BTW).

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

On Tue, Oct 9, 2012 at 10:35 AM, Jessica Streicher
<j.streicher at micromata.de> wrote:
> Can i somehow append objects to an .Rdata file?
>
> I didn't see an option for it in the save() method.
>
> dump() won't work since i have s4 objects in there.

I'm not sure I completely understand the issues you're trying to work
around, but I have two ideas for you.  One is a simple pseudo-append
function that loads the entire contents, adds the object, and saves
the result.  There are obviously memory issues with this strategy.

appendRData <- function(robj, filename) {

  tmpEnv <- new.env()

  savedObjects <- load(filename, envir = tmpEnv)

  # quick check for name collisions
  stopifnot(!(deparse(substitute(robj)) %in% savedObjects))

  save(list = c(savedObjects, deparse(substitute(robj))),
      file = filename,
      envir = tmpEnv)
}

A second possibility is to convert your RData files to a lazy-load
database as described by Simon Urbanek here:

http://stackoverflow.com/questions/8700619/get-specific-object-from-rdata-file
http://stackoverflow.com/questions/6550510/examining-contents-of-rdata-file-by-attaching-into-a-new-environment-possible

HTH


James