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)