Dear Matt,
Thanks very much for that quick and helpful reply -- I had wondered about
doing what you suggested, but had thought perhaps I could 'cut out the
middleman' of the imputed datasets and pull the matrices directly from
Amelia. Clearly not, so now I know how to go forward.
Many thanks and best wishes
Chris
At 02:08 17/08/2015, Matt Blackwell wrote:
Hi Chris,
There is no way to get those covariance matrices from R directly, but you
could calculate them from the imputed datasets and then average the
quantities together using the Rubin rules to produce estimates of the
covariance matrices and means. These imputed datasets are in the original
scales, so this should produce what you are looking for.
Cheers,
Matt
On Fri, Aug 14, 2015 at 4:39 AM Chris McManus
<i.mcmanus@ucl.ac.uk>
wrote:
- Hi -- I am new to this list, have tried searching for an answer
on
- the existing posts, and don't think there is one already, but
- apologies if I have missed it.
- My primary interest is in the estimated means and covariances
from
- the EM procedure (and bootstrapping helps as I need standard
errors
- of means, covariances, etc). It is clear that covMatrices and
mu are
- not on the original scale, and the JSS paper says on page 36
that
- "they refer to the variables after being transformed, centered
and scaled".
- The question is therefore, How do it get them on the original
scale?
- Is there a transformation matrix somewhere? Do I just alter the
means
- and SDs back to the original raw values, or has there been
a
- rotation of some sort as well? For my purposes I do need to
know the
- values on the raw scale measures. I guess I am missing
something
- here but am not sure what it is.
- Many thanks!
- Chris McManus
- University College London
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