Re: Fw: how to set smoothing parameter

From: Dennis Shea <shea_at_nyahnyahspammersnyahnyah>
Date: Mon Dec 30 2013 - 09:20:12 MST

Spectral analysis is as much art as it is science.

jave < 3
     Do no smoothing. spcx contains raw spectra estimates (periodogram).

     The degrees of freedom (df) associated with each estimate
     is two (2). Actually less than that if you have done tapering.
     These are issues with using the periodgram estimates.


It seems likely you do not have many data values.

jave = 3,5,7

     These give you roughly 6, 10, 14 df

     jave=3 means you can see finer
     detail (narrow bandwidth) but fewer df.

     jave=5,7 means you lose detail but get more
     statistical reliability

So, there is a trade-off and it is your responsibility
to decide which way to go.
Also, in cross spectral analysis, the coherence must be significant
On 12/30/13, 6:48 AM, 朱学明 wrote:
> Hi all,
>     I want to use the function specxy_anal(x,y,0,jave,0.1) to caculate the cross spectrum of two water transport's timeseries. But I don't know how to set the smoothing parameter jave to smooth the spectrum. Once change jave from 0 to 7, I have got very different results as followed in this e-mail.
>     Any clue to how to set the value for jave?
>     Thanks.
> 2013-12-24
> Xueming Zhu 朱学明
> Key Laboratory of Research on Marine Hazards Forecasting (LoMF), SOA
> National Marine Environmental Forecasting Center (NMEFC)
> No.8, Dahuisi Road, Haidian District, Beijing, 100081
> People's Republic of China
> Tel:+86-10-82481923
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Received on Mon Dec 30 09:20:23 2013

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