Hi Amelia users,
The reason I was hitting the website was to see if there was any
better documentation on the difference between the splinetime and
polytime options in Amelia.
My old code uses splinetime, and I have a comment saying "use
splinetime, not polytime", but I forget exactly why and it isn't well
documented in the PDF:
## polytime
integer between 0 and 3 indicating what power of polynomial should be
included in the imputation model to account for the effects of time. A
setting of 0 would indicate constant levels, 1 would indicate linear
time effects, 2 would indicate squared effects, and 3 would indicate
cubic time effects.
## splinetime
interger (sic) value of 0 or greater to control cubic smoothing
splines of time. Values between 0 and 3 create a simple polynomial of
time (identical to the polytime argument). Values k greater than 3
create a spline with an additional k-3 knot-points
To me that says splinetime is a superset of polytime (values k in
(0,1,2,3) are the same as polytime=k), which in turn implies to me
that polytime is there only for backwards compatibility. Is that
correct?
Regards,
James
--
James E. Marca, PhD
Researcher
Institute of Transportation Studies
AIRB Suite 4000
University of California
Irvine, CA 92697-3600
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