# Re: Unit of variance in spectral analysis

From: Hyacinth Nnamchi <hyacinth.1_at_nyahnyahspammersnyahnyah>
Date: Wed Jan 16 2013 - 07:08:00 MST

Hi Dennis,
That answers my question, thanks immensely.
Hyacinth

> Date: Tue, 15 Jan 2013 10:32:48 -0700
> From: shea@ucar.edu
> To: hyacinth.1@hotmail.com
> CC: ncl-talk@ucar.edu
> Subject: Re: Unit of variance in spectral analysis
>
> As noted in the function documentation:
> http://www.ncl.ucar.edu/Document/Functions/Built-in/specx_anal.shtml
>
> =======
> These spectra have been normalized so that the area under the curve:
>
> (spcx(0)+spcx(N/2-1))*(df/2) + SUM{spcx(1:N/2-2)*df}
>
> equals the variance of the detrended series, where df=(1/N)=frequency
> spacing.
>
> The units are variance/(unit frequency interval).
> ==========
>
>
> On 1/15/13 10:23 AM, Hyacinth Nnamchi wrote:
> >
> > Hi users,
> > The vertical axis of the spectral analysis examples (http://www.ncl.ucar.edu/Applications/spec.shtml) are labelled "variance". What is the unit? I'd think it represents the relative contributions of the different frequencies to the overall variance of the time series. But how is it scaled in ncl, as percents?
> > Hyacinth
> >
> >
> >
> >
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Received on Wed Jan 16 07:08:09 2013

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