mtmAR {astrochron} | R Documentation |
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.
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)
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) |
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
# 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)