[ncl-talk] Question about function - eofunc_varimax

[Dennis Shea]

I do not have much experience in performing REOF with the function.
I have attached the underlying fortran code that is used.
---
Also, user Jiang Ling contributed a variation to the 'varimax_dp.f'
That fortran code is also attahed.

I hope that helps.
D

On Thu, May 30, 2019 at 12:25 PM Chi-Hung Chang <jack7989 at gmail.com> wrote:

> Dear all,
>
> I have used function *eofunc_varimax *to obtain rotated EOFs of my data,
> but there are some questions as follow that I would like to clarify :
>
> (a) There are three options to choose by setting up *optEVX as*
>      0 => do nothing; use the normalized eigenvectors directly.
>      1 => scale the normalized eigenvectors by the square root of the
> associated eigenvalue and return normalized eigenvectors.
>
>     -1 => same as *optEVX*=1 but returns the scaled rotated eigenvectors.
>
> My comprehension is that, by setting up *optEVX *as 1 or -1, it first
> *denormalizes* the input EOF calculated by function *eofunc* (since by
> default, the output of *eofunc *is normalized EOF). Is my understanding
> correct?
>
> (b) By setting *optEVX = 1*, the output rotated EOF is normalized by
> dividing with square root of corresponding rotated eigenvalues, while it is
> not normalized if setting  *optEVX = -1*
>
> (c) How does the *varimax_variance *and corresponding *percent variance
> explained* are calculated? I have read the reference textbook Statistical
> Method in Atmospheric Sciences but still can't find the answer.
>
> It would be a great help if anyone who has experience in performing REOF
> and this function could guide me :)
>
> Really appreciate your help.
>
> Best,
>
>
> Jack Chi-Hung Chang, Ph.D. Student
>
> Research Assistant
> National Center for Airborne Laser Mapping
> University of Houston
>
> cchang21 at uh.edu
>
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