astrochron (version 1.4)

asm: Average Spectral Misfit

Description

Calculate Average Spectral Misfit with Monte Carlo spectra simulations, as updated in Meyers et al. (2012).

Usage

asm(freq,target,fper=NULL,rayleigh,nyquist,sedmin=1,sedmax=5,numsed=50,
    linLog=1,iter=100000,output=F,genplot=T)

Value

A data frame containing: Sedimentation rate (cm/ka), ASM (cycles/ka), Null hypothesis significance level (0-100 percent), Number of astronomical terms fit.

Arguments

freq

A vector of candidate astronomical cycles observed in your data spectrum (cycles/m). Maximum allowed is 500.

target

A vector of astronomical frequencies to evaluate (1/ka). These must be in order of increasing frequency (e.g., e1,e2,e3,o1,o2,p1,p2). Maximum allowed is 50 frequencies.

fper

A vector of uncertainties on each target frequency (1/ka). Values should be from 0-1, representing uncertainty as a percent of each target frequency. The order of the uncertainties must follow that of the target vector. By default, no uncertainty is assigned.

rayleigh

Rayleigh frequency (cycles/m).

nyquist

Nyquist frequency (cycles/m).

sedmin

Minimum sedimentation rate for investigation (cm/ka).

sedmax

Maximum sedimentation rate for investigation (cm/ka).

numsed

Number of sedimentation rates to investigate in ASM optimization grid. Maximum allowed is 500.

linLog

Use linear or logarithmic scaling for sedimentation rate grid spacing? (0=linear, 1=log)

iter

Number of Monte Carlo simulations for significance testing. Maximum allowed is 100,000.

output

Return output as a new data frame? (T or F)

genplot

Generate summary plots? (T or F)

Details

This function will caculate the Average Spectral Misfit between a data spectrum and astronomical target spectrum, following the approach outlined in Meyers and Sageman (2007), and the improvements of Meyers et al. (2012).

References

S.R. Meyers and B.B. Sageman, 2007, Quantification of Deep-Time Orbital Forcing by Average Spectral Misfit: American Journal of Science, v. 307, p. 773-792.

S.R. Meyers, B.B. Sageman and M.A. Arthur, 2012, Obliquity forcing of organic matter accumulation during Oceanic Anoxic Event 2: Paleoceanography, 27, PA3212, doi:10.1029/2012PA002286.

See Also

eAsm, eAsmTrack, testPrecession, timeOpt, and timeOptSim

Examples

## These frequencies are from modelA (type '?astrochron' for more information). 
## They are for an 8 meter window, centered at 22 meters height. Units are cycles/m . 
freq <- c(0.1599833,0.5332776,1.5998329,2.6797201,3.2796575,3.8795948,5.5194235,6.5459830)
freq <- data.frame(freq)

## Rayleigh frequency in cycles/m
rayleigh <- 0.1245274

## Nyquist frequency in cycles/m
nyquist <- 6.66597

## orbital target in 1/ky. Predicted periods for 94 Ma (see Meyers et al., 2012)
target <- c(1/405.47,1/126.98,1/96.91,1/37.66,1/22.42,1/18.33)

## percent uncertainty in orbital target
fper=c(0.023,0.046,0.042,0.008,0.035,0.004)

asm(freq=freq,target=target,fper=fper,rayleigh=rayleigh,nyquist=nyquist,sedmin=0.5,sedmax=3,
    numsed=100,linLog=1,iter=100000,output=FALSE)