mtmAR {astrochron}

Intermediate spectrum test of Thomson et al. (2001)

Description

Perform the 'intermediate spectrum test' of Thomson et al. (2001).

Paraphrased from Thomson et al. (2001): Form an intermediate spectrum by dividing MTM by AR estimate. Choose an order P for a predictor. A variety of formal methods are available in the literature, but practically, one keeps increasing P (the order) until the range of the intermediate spectrum Si(f) (equation (C4) of Thomson et al., 2001) stops decreasing rapidly as a function of P. If the intermediate spectrum is not roughly white, as judged by the minima, the value of P should be increased.

Usage

mtmAR(dat,tbw=3,ntap=NULL,order=1,method="mle",CItype=1,padfac=5,demean=T,detrend=F,
      output=1,xmin=0,xmax=Nyq,pl=1,genplot=T,verbose=T)

Arguments

dat

Stratigraphic series for analysis. First column should be location (e.g., depth), second column should be data value.

tbw

MTM time-bandwidth product.

ntap

Number of DPSS tapers to use. By default, this is set to (2*tbw)-1.

order

Order of the AR spectrum.

method

AR method ("yule-walker", "burg", "ols", "mle", "yw")

CItype

Illustrate (1) one-sided or (2) two-sided confidence intervals on plots

padfac

Pad with zeros to (padfac*npts) points, where npts is the original number of data points.

demean

Remove mean from data series? (T or F)

detrend

Remove linear trend from data series? (T or F)

output

Output (1) intermediate spectrum and confidence levels, (2) intermediate spectrum, (3) confidence levels

xmin

Smallest frequency for plotting.

xmax

Largest frequency for plotting.

pl

Plot logarithm of spectral power (1) or linear spectral power (2)?

genplot

Generate summary plots? (T or F)

verbose

Verbose output? (T or F)

References

Thomson, D. J., L. J. Lanzerotti, and C. G. Maclennan, 2001, The interplanetary magnetic field: Statistical properties and discrete modes, J. Geophys.Res., 106, 15,941-15,962, doi:10.1029/2000JA000113.

See Also

eha, lowspec, mtm, mtmML96, periodogram, and spec.mtm

Examples

# generate example series with periods of 400 ka, 100 ka, 40 ka and 20 ka
ex = cycles(freqs=c(1/400,1/100,1/40,1/20),start=1,end=1000,dt=5)

# add AR1 noise
noise = ar1(npts=200,dt=5,sd=.5)
ex[2] = ex[2] + noise[2]

# MTM spectral analysis, with conventional AR1 noise test
pl(1,title="mtmAR")
mtmAR(ex)