timeOptSim {astrochron}R Documentation

Monte Carlo simulation for TimeOpt

Description

Perform Monte Carlo AR1 simulations to evaluate significance of TimeOpt results, as in Meyers (2015).

Usage

timeOptSim(dat,numsim=2000,rho=NULL,sedrate=NULL,sedmin=0.5,sedmax=5,numsed=100,
         linLog=1,limit=T,fit=1,fitModPwr=T,flow=NULL,fhigh=NULL,roll=NULL,
         targetE=NULL,targetP=NULL,detrend=T,ncores=2,output=0,genplot=T,
         check=T,verbose=T)
 

Arguments

dat

Stratigraphic series for astrochronologic assessment. First column should be depth or height (in meters), second column should be data value.

numsim

Number of Monte Carlo AR1 simulations.

rho

AR1 coefficient to use in simulations. By default this will be estimated from the stratigraphic series.

sedrate

Sedimentation rate for investigation (cm/ka). This options is for compatibility with prior versions of timeOptSim. Please use sedmin, sedmax, numsed.

sedmin

Minimum sedimentation rate for investigation (cm/ka).

sedmax

Maximum sedimentation rate for investigation (cm/ka).

numsed

Number of sedimentation rates to investigate in optimization grid.

linLog

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

limit

Limit evaluated sedimentation rates to region in which full target signal can be recovered? (T or F)

fit

Test for (1) precession amplitude modulation or (2) short eccentricity amplitude modulation?

fitModPwr

Include the modulation periods in the spectral fit? (T or F)

flow

Low frequency cut-off for Taner bandpass (half power point; in cycles/ka)

fhigh

High frequency cut-off for Taner bandpass (half power point; in cycles/ka)

roll

Taner filter roll-off rate, in dB/octave.

targetE

A vector of eccentricity periods to evaluate (in ka). These must be in order of decreasing period, with a first value of 405 ka.

targetP

A vector of precession periods to evaluate (in ka). These must be in order of decreasing period.

detrend

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

ncores

Number of cores to use for parallel processing. Must be >=2

output

Which results would you like to return to console? (0) no output; (1) p-value; (2) simulation r2 results

genplot

Generate summary plots? (T or F)

check

Conduct compliance checks before processing? (T or F). In general this should be activated.

verbose

Verbose output? (T or F)

Details

TimeOpt is an astronomical testing algorithm for untuned (spatial) stratigraphic data. The algorithm identifies the sedimentation rate(s) that simultaneously optimizes: (1) eccentricity amplitude modulations within the precession band, and (2) the concentration of spectral power at specified target astronomical periods. The statistical significance of the r^2_opt is determined via Monte Carlo simulation using timeOptSim.

The present version of timeOptSim improves upon the original significance testing method of Meyers (2015), by conducting simulations across the entire sedimentation grid. This approach more rigorously protects against inflation of the p-value due to multiple testing. Parallel processing has been implemented to address the greater computational demand that is required.

See timeOpt for more information on the basic methodology.

References

S.R. Meyers, 2015, The evaluation of eccentricity-related amplitude modulations and bundling in paleoclimate data: An inverse approach for astrochronologic testing and time scale optimization: Paleoceanography.

See Also

asm, eAsm, eAsmTrack, testPrecession, timeOpt, and timeOptPlot

Examples

 ## Not run: 
# generate a test signal with precession and eccentricity
ex=etp(tmin=1,tmax=1000,dt=5,pWt=1,oWt=0,eWt=1,esinw=TRUE,genplot=FALSE,verbose=FALSE)
# convert to meters with sedimentation rate of 2 cm/kyr
ex[1]<-ex[1]*0.02
# evaluate with timeOptSim. be patient, this may take a while to run.
timeOptSim(ex,sedmin=0.5,sedmax=5,numsed=100)
 
## End(Not run)

[Package astrochron version 1.1 Index]