st: R: imputation of missing dates

["Carlo Lazzaro" <carlo.lazzaro@tin.it>]

Yulia may want to take a look at the following articles:

Royston, P. 2004. Multiple imputation of missing values. Stata Journal 4(3):
227?241.
Royston, P. 2005. Multiple imputation of missing values: update. Stata
Journal 5(2): 1?14.

However, I am not clear about the reason why some patients did not attend to
the examination, although invited to. 
Did they move away from the study? 
Are they substantially different for other covariates when compared to
participants?

Kindest Regards,
Carlo
-----Messaggio originale-----
Da: owner-statalist@hsphsun2.harvard.edu
[mailto:owner-statalist@hsphsun2.harvard.edu] Per conto di Yulia Blomstedt
Inviato: giovedì 5 maggio 2011 16.29
A: statalist@hsphsun2.harvard.edu
Oggetto: st: imputation of missing dates

Dear Statalist,
I need to impute the missing data in a dataset by matching it to the
already existing data. I have never worked with either imputation or
matching and am at a loss. I would deeply appreciate any advice.
My dataset contains background data for individuals who participated
in a medical examination (i.e., ?participants?) and who did not
participate in the examination (?non-participants?) between 1990-2006.
All individuals were invited to participate in the examination when
they reached a certain age. The examination usually took place during
the same year as they reached that age between mid-January and  the
end of June or between August and mid-December.
I have the following data: the year (yyyy) when the individuals were
invited to participate in the examination (YEAR) and the exact date
(yyyymmdd) when the ?participants? have participated in the
examination (EXAMDATE).
I need to create an EXAMDATE for ?non-participants?, the date when
they could have participated in the examination. How do I do it?
The EXAMDATE of ?non-participants? should have the same
range/distribution as among the ?participants?, i.e., it should be
between mid-January and the end of June or between August and
mid-December during the year when a ?non-participant? was invited to
the examination.
Thank you in advance for your help.
Yulia

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