Calculates spectra quantities of a series.

**Note:** This function is only available in version 4.1.1 of
NCL. If your site is licensed for version 4.1, then you can get
version 4.1.1 for free. To get version 4.1.1 of NCAR Graphics
software, please contact your site representative. If you don't know
who your site representative is, then send email to ncarginf@ucar.edu or call (303)
497-1201.

function specx_anal( x : float, iopt : integer, jave : integer, pct : float )

*x*- A 1-dimensional array of length
*N*containing the data. Missing values are not allowed. *iopt*- detrending option. iopt = 0 => remove series mean, iopt = 1 => remove the series mean and least squares linear trend.
*jave*- smoothing to be performed on the periodiogram estimates. This should
be an odd number (>= 3). If not, the routine will force it to
the next largest odd number.
jave=0 : do no smoothing spcx contains raw spectra estimates (periodogram) jave>0 : average jave periodogram estimates together utilizing modified daniell smoothing (good stability but may lead to large bias ). all weights are 1/jave except wgt(1) and wgt(jave) which are 1/(2*jave). this is the recommended option. It is this number which has the most impact on the degrees of freedom.

*pct*- percent of the series to be tapered (0.0 <= pct <= 1.0). If
*pct*=0.0, no tapering will be done. If*pct*= 1.0, the whole series is effected. A*pct*of 0.10 is common (tapering should always be done).

*spcx*- 1-dimensional array of length N/2

spcx(0) - spectral estimate at frq = (1/N) [N=dimsizes(x)]

spcx(N/2-1)- spectral estimate at frq = 0.5These spectra have been normalized so that SUM{spcx(n)*df}= variance of the detrended series where df=frequency spacing. The units are variance/(unit frequency interval).

*frq*- frequency (cycles/time). A 1-dimensional array of length*N*/2.*bw*- spectral band width (scalar, float)*xavei*- average of the x series on input (scalar, float)*xvari*- variance of the x series on input (scalar, float)*xvaro*- variance of the x series after detrending (scalar, float)*xlag1*- lag one auto correlation of the x series after detrending (scalar, float)*xslope*- least squares slope per time interval of linear trend (if*iopt*= 1) of the x series.

iopt = 0 ; remove series mean jave = 0 ; no smoothing; return periodogram estimates pct = 0.1 ; taper 10% of the data dof = specx_anal (x,iopt,jave,pct)

iopt = 0 ; remove series mean jave = 3 ; Average 3 periodogram estimates using modified Daniel pct = 0.1 ; taper 10% of the data dof = specx_anal (ndtooned(x),iopt,jave,pct)

iopt = 1 ; remove least squares linear trend in x ; prior to tapering and computing spectra. jave = 5 ; Average 5 periodogram estimates using modified Daniel pct = 0.1 ; taper 10% of the data dof = specx_anal (x(lev|kl:kl,lat|nl:nl,lon|ml:ml,time:),iopt,jave,pct)

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