st: separate multiple imputations within the same dataset

["Neal Traven" <traven@u.washington.edu>]

Hello StataList,

I have a fairly large dataset (about 10K records) containing healthcare data 
from both pre-hospital and hospital settings.  Since I don't have Stata11, 
I'm using -ice- for multiple imputation.

My problem is that I want do two separate imputation runs in the same 
dataset -- one that uses the pre-hospital variables to impute missing 
pre-hospital data, and one that uses hospital variables to impute missing 
hospital data.  Each of those imputation runs could also use patient data 
(age, gender, etc.).  Though I haven't thought it through yet, I might also 
want to use some of the pre-hospital variables as predictors in the hospital 
imputations; for example, whether a patient was intubated on the way to the 
hospital might affect some of the hospital variables.

If I use the -m()- option to do, say, 5 imputations on the pre-hospital 
variables, how can I use those results for the hospital variables?  I don't 
want to make a dataset with 36 times the original size of the dataset 
(that's the original plus 5 imputed datasets, squared).

What I would really like to be able to do is to run both imputations in a 
single Stata command, telling it to use the pre-hospital variables for 
pre-hospital imputation and the hospital variables for hospital imputation 
... at the same time.

Is that possible?  Is there some way to do this?  Am I making any sense at 
all?

----------
Neal D. Traven, PhD
Research Consultant
Harborview Injury Prevention & Research Center
325 Ninth Ave, Box 359960, Seattle WA  98104-2499
206-744-9459, www.hiprc.org

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