20 Feb
2008
20 Feb
'08
9:45 a.m.
Wow, that was fast. Thank you, Matt!
Alright, that tells me that "idvars" may be used for, e.g., IDs, contact
info (like email) in survey data and so on... stuff that has no
statistical relevance whatsoever.
But, on the other side, I would not put "perfect data columns" (i.e. no
NAs) as idvars, because they would just deteriorate the MI process.
That also means that ALL columns (except idvars) in a data frame ARE
used by Amelia, either to be imputed or to be utilized for imputation
elsewhere.
I am pointing that out because I am very new to Amelia/MI -- and am
already preparing another question related to the ords and noms
parameters and related error messages I am getting. :-)
Regards,
Marcus
Am 20.02.2008 15:27 schrieb Matt Blackwell:
Hello Marcus,
The identification vars are removed from the dataset before the
algorithm is run and returned to their rightful columns once the
algorithm has finished. Thus, (b) is the correct answer. You would get
the same results from Amelia if you sent it your data with those ID
columns removed.
good luck,
matt.
On Feb 20, 2008 9:23 AM, Marcus M. Dapp <mdapp(a)ethz.ch> wrote:
> Hello
>
> The manual says about identification variables: "idvars : a vector of
> column numbers or column names that indicates identification variables.
> These will be dropped from the analysis but copied into the imputed
> datasets."
>
> The "dropping" is not 100% clear to me in an important aspect, namely,
> whether idvars are -considered- in the MI calculation process at all. So
> is a) or b) the correct answer?
>
> a) The idvars are -used- in the MI process to calculate imputations, but
> are themselves not modified (imputed). They are copied to the output
> dataset 1:1.
>
> b) The idvars are only copied and -not- (even) considered in the MI
> process to calculate imputations.
>
> Thank you,
> Marcus
>
> --
>
> Marcus M. Dapp | PhD student | ETH Zurich | www.ib.ethz.ch/people/mdapp
> Prof. Thomas Bernauer, International Relations | www.ib.ethz.ch
>
> On the shoulders of giants? http://science.creativecommons.org
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>
--
Marcus M. Dapp | PhD student | ETH Zurich | www.ib.ethz.ch/people/mdapp
Prof. Thomas Bernauer, International Relations | www.ib.ethz.ch
On the shoulders of giants? http://science.creativecommons.org
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