mtmAR {astrochron} R Documentation

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.

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)

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)


[Package astrochron version 1.1 Index]