Hi Ruben, 

There are few strange things that maybe you can clarify. First, you've asked Amelia for 1 imputation in the second approach, so I'm not sure why there would be more than 1 imputed dataset in the "imputations" list. Next, can you send along your environment (OS type, version, R version, etc, foreach backend) and the error messages you are receiving?

I wonder if this is a problem with the specific dataset. Can you see if Amelia works with the example data? 

library(Amelia)
data(africa)
a.out <- amelia(africa, ts = "year", cs = "country", parallel = "multicore", m = 1,ncpus = parallel::detectCores())

If that fails again, I would try to reinstall Amelia either from source or even better from a binary if you are on Mac OS X or Windows. 

Hope that helps!

Cheers,
matt.

~~~~~~~~~~~
Matthew Blackwell
Assistant Professor of Political Science
University of Rochester
url: http://www.mattblackwell.org


On Thu, Feb 14, 2013 at 10:25 AM, Ruben Arslan <rubenarslan@gmail.com> wrote:
Dear list,

I installed 1.7 from source from the Cran repo to try out parallel
imputation.
Before 1.7 I did it with foreach
mtfs_i <- foreach(i=1:5,.combine="ameliabind",.inorder=F) %dopar% { 
amelia(mtfs, 
m = 1, 
)
}
and it worked fine.

with 1.7 I tried using multicore using the parallel argument.

mtfs_i <- amelia(mtfs, 
m = 1, 
parallel = "multicore", # note: this will crash R if tcltk is loaded prior to 2.15.3
ncpus = parallel::detectCores(), 
)

Both approaches finish without error, but I get a messed-up S3 object.
So, in approach 1 using foreach ameliabind complains that it didn't get amelia objects.

With approach 2 I get a list of Amelia objects, but the first two items are NULL and I don't get one list $imputations with many imputations, but a stitched-up object. 
Using this object with e.g. transform or overimpute fails, but doing the same with the third object in the list works (that's just one imputation then though).

Regards,

Ruben Arslan

student assistant
Lab: http://www.psychology.hu-berlin.de/profship/perdev
Humboldt-University of Berlin
Unter den Linden 6
10099 Berlin, Germany


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