It might be that you have identified a fully observed variable as
something to be imputed (you could try it without it), but I'm not
positive. I'm forwarding this to the new Amelia listerv. Maybe one of my
colleagues or someone else can help?
Gary
On Tue, 30 Apr 2002, bob wrote:
Gary,
Thanks for your earlier reply re: Amelia. I think we have cleared up the
working space problem.
Now another challenge confronts us.
During stage 1 of 4, (EM), the program bombs after iteration 34, and gives
the message, "sweep: elements of m cannot be zero. Exec stopped in line
79."
I have run this twice to make sure I had checked the correct global commands
for the correct variablres. The program was using the conditional model. 2
variables are fully obserfed, and 1 is nominal. The 12 category "Country"
variable is both fully observed and nominal.
Does the error message have something to do with this?
Presently, there are 37 variables, and just over 20,000 observations.
This is not time series data, but should both Country, as well as
Rural/Urban be identified as cross sections?
Any help you can give would be greatly appreciated.
Regards,
Bob Mattes
----- Original Message -----
From: Gary King <king(a)harvard.edu>
To: mike <mike(a)idasact.org.za>
Cc: <ajoseph(a)fas.harvard.edu>du>; <tercer(a)latte.harvard.edu>du>;
<kscheve(a)latte.harvard.edu>du>; Robert Mattes <bob(a)idasact.org.za>
Sent: Thursday, March 28, 2002 3:05 PM
Subject: Re: your mail
have a look at this:
http://gking.harvard.edu/amelia/node55.html
I think it will answer your question.
Gary King
: Gary King, King(a)Harvard.Edu
http://GKing.Harvard.Edu :
: Center for Basic Research Direct (617) 495-2027 :
: in the Social Sciences Assistant (617) 495-9271 :
: 34 Kirkland Street, Rm. 2 HU-MIT DC (617) 495-4734 :
: Harvard U, Cambridge, MA 02138 eFax (928) 832-7022 :
On Thu, 28 Mar 2002, mike wrote:
> Dear Gary King,
>
> This follows up on the message I left on your voice-mail earlier today.
>
> I'm a political scientist from Michigan State University who, with
Robert Mattes of the University of Cape Town, co-directs the Afrobarometer.
The Afrobarometer is a large-scale, cross-national survey research project
on public attitudes to democracy and markets in 12 African countries.
>
> We are currently analyzing a fairly large data set (150 variables x
21,000
cases) from Round 1 of the Afrobarometer. It contains quite a bit of
missing data, both randomly distributed and country specific. On the advice
in the AMELIA manual, we have cut down on missingness by rescaling "don't
knows". We have also reduced the core variables for analysis to 37 before
trying to implement AMELIA.
>
> Our basic problem is that AMELIA will not run when we include all 21,000
cases. It keeps giving us an error message that says "insufficient
workspace memory". We can get AMELIA to generate 5 imputed data sets for a
sub-sample of 2000 cases. It takes about half an hour. And we can get
AMELIA to complete the iterations in Step 1 on 5,000 cases. But the program
bombs in Step 2 when it tries to impute covariances (after about 45
minutes), again yielding the same error message. Attempts at 10,000 and
21,000 will not even start running.
>
> We have here a Pentium 4 computer with 1 Ghtz hard drive and 256 mg free
RAM
and 20 Gbyte disk.
>
> Our questions are as follows:
>
> * Is there a limit to the number of cases that AMELIA can handle? Will
it
work on a data set of 37 variables by 21,000 cases?
>
> * Does the error message refer to AMELIA's workspace or the computer's
workspace? In other words, does the problem lie in the capacity of the
hardware or the software?
>
> * If we include a 12-value multinomial variable for "country", does
this take us over AMELIA's limit of 40 variables? We have tried to run the
program both with and without this variable, with the same problematic
result.
>
> * For your information, we have specified one nominal variable
(country,
when included) and two fully observed variables (one of which is
country, when included).
>
> We will make one more effort to call you today before Cape Town closes
down
for Easter. In case you want to call, you can reach us at 011 27 83
234 0333. I have copied this message to your associates at Harvard in case
you aren't in this week. If we have not spoken today, would you be so kind
as to reply by e-mail, with a copy to bob(a)idasact.org.za.
>
> With many thanks for your time. We look forward to using your valuable
program.
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