[R] Ignoring loadNamespace errors when loading a file

[Uwe Ligges]

On 22.08.2011 08:52, Allan Engelhardt wrote:
> On a Unix machine I ran caret::rfe using the multicore package, and I
> saved the resulting object using save(lm2, file = "lm2.RData").
> [Reproducible example below.]
>
> When I try to load("lm2.RData") on my Windows laptop, I get
>
> Error in loadNamespace(name) : there is no package called 'multicore'
>
> I completely understand the error and I would like to ignore it and
> still load the saved object data.
>
> I imagine that I can make myself an empty multicore package for Windows
> and load the data file successfully, but is there another way?
>
> (I am not going to use any multicore functionality; I just want to
> inspect some of the data stored in the object and the reference in
> question is just an unfortunately stored link from the original call.)
>
> (I did search for this question in the archives, but could only find it
> discussed in connection with starting R with a .RData file where the
> consensus seems to be to start R in vanilla mode and install the missing
> package. This situation is different and installing a Unix-only package
> on Windows is obviously a non-starter, except as I proposed above.)
>
> Obligatory reproducible example: On the Unix machine do
>
> library("multicore")
> a <- list(data = 1:10, fun = mclapply)
> save(a, file = "a.RData")
>
> and then try to load the "a.RData" file on Windows. The question is if I
> can recover the data (1:10) on that platform.

Short answer: No.

The element "fun" within "a" relies on the Namespace being present. And 
then you want additionally just part of an object. If this is really 
relevant, you have to digg into ./src/main/saveload.R and serialize.R 
and try to write your own interface to extract parts of objects. So this 
is probably not worth the effort.

Uwe Ligges



> Allan
>
>> sessionInfo()
> R version 2.13.1 (2011-07-08)
> Platform: x86_64-pc-mingw32/x64 (64-bit)
>
> locale:
> [1] LC_COLLATE=English_United Kingdom.1252
> [2] LC_CTYPE=English_United Kingdom.1252
> [3] LC_MONETARY=English_United Kingdom.1252
> [4] LC_NUMERIC=C
> [5] LC_TIME=English_United Kingdom.1252
>
> attached base packages:
> [1] compiler stats graphics grDevices utils datasets methods
> [8] base
>
> other attached packages:
> [1] caret_4.98 cluster_1.14.0 reshape_0.8.4 plyr_1.6
> [5] lattice_0.19-31 boot_1.3-2 ctv_0.7-3
>
> loaded via a namespace (and not attached):
> [1] grid_2.13.1 tools_2.13.1
>
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