Re: EOF signs

Not sure what to say. The EOF signs are entirely arbitrary.
To my knowledge, there is no way to precondition
the input data to force a particaular sign convention.

Aideen Foley wrote:
> Thank you both for your responses.
> It is useful to know how this point testing can be accomplished, but for
> my purposes it is not ideal. For comparative purposes I would prefer to
> apply the same methodology to all datasets rather than adjusting some
> and not others.
> If you have any further thoughts on the matter, please let me know.
> Regards,
> Aideen
>
>
> On Wed, Sep 9, 2009 at 4:19 PM, Dennis Shea <shea_at_ucar.edu
> <mailto:shea_at_ucar.edu>> wrote:
>
> To add a bit more information:
>
> Consider EOF(neof,lat,lon) and you want the
> first EOF over (say) Iceland to be negative
>
> if (EOF(0,{64},{340}).gt.0) then
> EOF(0,:,:) = -EOF(0,:,:) ; switch all signs
> end if
>
>
>
>
>
>
> Wei Huang wrote:
>
> Aideen,
>
> There is no way to have the EOFs automatically
> give the same sign. The EOFs are calculated using
> LAPACK's "dspevx" routine.
>
> If there is a location in space that you want a
> particular sign, you could test that point and
> change the sign accordingly.
>
> Regards,
>
> Wei Huang
> huangwei_at_ucar.edu <mailto:huangwei_at_ucar.edu>
> <mailto:huangwei_at_ucar.edu <mailto:huangwei_at_ucar.edu>>
>
> VETS/CISL
> National Center for Atmospheric Research
> P.O. Box 3000 (1850 Table Mesa Dr.)
> Boulder, CO 80307-3000 USA
> (303) 497-8924
>
>
>
>
>
> On Sep 9, 2009, at 7:44 AM, Aideen Foley wrote:
>
> Hello.
> I am applying the same EOF analysis script to output from
> different climate models, and finding that for some
> datasets, the primary EOF is positive, and for others it is
> negative, with a time amplitude series that is the inverse
> of what I would expect were it positive. I know that that
> one can multiply the EOF and it's time amplitude series by
> -1 to aid interpretation, but I would like to understand why
> the eofunc routine prefers inverted output for some of my
> data but not for others. I would like if it followed the
> same convention with each. dataset. Can anyone help me with
> this question?
> Many thanks,
> Aideen Foley
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Received on Fri Sep 11 2009 - 05:58:58 MDT