[R] Question about object permanence/marshalling

[jim holtman]

The problem I think is in your unmarshal.  'load' will load the object
into the local environment, not the global.  You have to explicitly
return it, that means you have to know the name that its was 'save'd
by;

> unmarshal <- function(xdr) {
>     object <- strsplit(strsplit(xdr, "\\.")[[1]][[1]], "/")
>     object <- object[[1]][length(object[[1]])]
>     load(xdr)
>     print(sprintf("Loading %s", xdr))
       ?????  # return the object that was just loaded; don't know if
they all have the same name.
>     }




On Thu, Aug 25, 2011 at 9:34 AM, Albert-Jan Roskam <fomcl at yahoo.com> wrote:
> Hello,
>
> I am trying to write some code that dumps R objects to the harddisk in a binary format so they can be quickly re-used later. Goal is to save time. The objects may be quite large (e.g. classes for a GUI). I was thinking that save() and load() would be suitable for this (until now I only thought it could be used for 'real' data, e.g. matrices, data.frames etc), but I am hoping any object can be 'marshalled' using these functions. Probably I am doing something wrong in the unmarshal() function, perhaps with assign().
>
> Thank you in advance!
>
> AJ
>
>
> #########
> # Creation of test data
> #########
> setClass(
>   Class="Test",
>     representation=representation(
>       amounts="data.frame"
>       )
> )
> setMethod(
>   f="initialize",
>   signature="Test",
>   definition=function(.Object, amounts){
>     .Object at amounts <- amounts
>     return(.Object)
>   }
> )
> setGeneric (
>   name="doStuff",
>   def=function(.Object){standardGeneric("doStuff")}
> )
> setMethod(
>   f = "doStuff",
>   signature = "Test",
>   definition=function(.Object) {
>     return(mean(.Object at amounts, na.rm=TRUE))
>   }
> )
>
> print( objects() )
> instance <- new(Class="Test", data.frame(amount=runif(10, 0, 10)))
> doStuff(instance)
>
> #########
> # actual code (incomplete)
> #########
> marshal <- function(object) {
>     fn <- file.path(Sys.getenv()["TEMP"], paste(object, ".xdr", sep=""))
>     save(object, file=fn, compress=FALSE)
>     print(sprintf("Saving %s", fn))
>     }
> unmarshal <- function(xdr) {
>     object <- strsplit(strsplit(xdr, "\\.")[[1]][[1]], "/")
>     object <- object[[1]][length(object[[1]])]
>     assign(object, load(xdr))
>     print(sprintf("Loading %s", xdr))
>     }
> print(objects())
> lapply(c("doStuff", "instance"), marshal)
> rm(list=c("doStuff", "instance"))
>
> xdrs <- Sys.glob(file.path(Sys.getenv()["TEMP"], "*.xdr"))
> lapply(xdrs, unmarshal)
> print(objects())  ## doStuff and instance do not appear! :-(
>
>
> Cheers!!
> Albert-Jan
>
>
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>



-- 
Jim Holtman
Data Munger Guru

What is the problem that you are trying to solve?