Mike and others,
This is a follow-up to my posting yesterday regarding eof_varimax. In
that I described an empirical procedure to calculate percentage variance
of rotated EOFs. I am afraid that procedure is not right, due to the
loss of orthogonality (space or time) after rotation of EOFs. So, please
disregard that message.
saji
Saji N. Hameed, Assistant Researcher,
IPRC-SOEST, 2525 Correa Road, Univ. of Hawaii,
Honolulu, HI 96822, U.S.A
http://iprc.soest.hawaii.edu/~saji
tel.: (808) 956 9534 , fax.: (808) 956 9425
>
> Today's Topics:
>
> 1. Re: ncl-talk Digest, Vol 16, eofunc_varimax (Saji Hameed)
> 2. accounting for surface area differences when averaging
> (Cathryn Meyer)
> 3. Re: accounting for surface area differences when averaging
> (Adam Phillips)
>
>
> --------------------------------------------------------------------
> --
>
> Message: 1
> Date: Thu, 17 Mar 2005 10:58:38 -1000
> From: Saji Hameed <saji@hawaii.edu>
> Subject: Re: ncl-talk Digest, Vol 16, eofunc_varimax
> To: ncl-talk@ucar.edu
> Message-ID: <11ffbe11bdf2.11bdf211ffbe@hawaii.edu>
> Content-Type: text/plain; charset=us-ascii
>
> Mike,
>
> Jing has given you part of the answer. I will try to fill up what she
> has not mentioned.
>
> I have not tried this, but i have no reason to believe why it
> should not
> work.
>
> 1. eofunc_ts should be able to return your time series after varimax
> rotation, the same way it does return the time series for the
> unrotatedeofs. I guess this function regresses (evec) on (data) to
> obtain the
> time series.
>
> 2. You can always calculate the percentage variance explained by a
> pattern once you have (evec) and its corresponding time series and of
> course the data.
>
> a- sum up the variance in the (data) over the same domain that
> you had specified to the eof- functions.
>
> b- calculate the variance associated with each (evec) pattern.
> To do this multiply evec with the time series, find the
> variance and sum it up over the domain
>
> c - (b/a)*100 is the percentage variance associated with each
> pattern.
>
>
> A grads script that can do varimax can be found at
>
> http://mpi-web.dkrz.de/en/misc/software/grads/varimax.gs
>
>
> saji
>
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