Precession constant from the RATIO of two cycles in one section
Source:R/k_from_ratio.R
k_from_ratio.RdScale-free: the ratio of two cycle periods equals the ratio of the two wavelengths, so this works on an untuned depth series just as well as on a tuned record, and no sedimentation rate is needed. Solving T1/T2 = (p + f2)/(p + f1) for the precession frequency p gives p = (f2 - R f1) / (R - 1), R = T1/T2, T1 > T2.
Usage
k_from_ratio(
long,
short,
term_long = "k+s3",
term_short = "k+g5",
age_ma,
rel_sd = 0.03,
record_length = NULL,
mult = 1,
nsim = 20000,
method = c("angular_momentum", "astrogeo22"),
seed = NULL,
data_dir = NULL
)Arguments
- long
Period of the longer of the two cycles (numeric, >
short), in kyr for a tuned record or in metres for a depth series; only the ratiolong / shortis used. Required (no default).- short
Period of the shorter cycle, in the same unit as
long(numeric, > 0). Required (no default).- term_long
Astronomical term of the longer cycle (character), e.g.
"k+s3"(obliquity),"k+g5"(precession) or an eccentricity term such as"e405","e125","e95"(seeastro_terms). At least one of the two terms must contain k.Default="k+s3".- term_short
Astronomical term of the shorter cycle (character), with the same options as
term_long.Default="k+g5".- age_ma
Age of the record in Ma (numeric, one value or
c(min, max), of which the mean is used); sets the obliquity used byctest_earthmoonand the AstroGeo22 reference values. Required (no default).- rel_sd
Relative one-sigma uncertainty of each measured cycle (numeric, >= 0; 0.03 is 3%); the cycles are drawn from normal distributions. Ignored when
record_lengthis given.Default=0.03.- record_length
Length of the analysed record in the same unit as the cycles (numeric, > 0). If given, each cycle is drawn uniformly from the band set by the frequency resolution
mult / record_length(seecycle_band) instead of usingrel_sd.Default=NULL.- mult
Multiple of the frequency resolution used as half-width of the band when
record_lengthis given (numeric, > 0).Default=1.- nsim
Number of Monte Carlo draws (integer, >= 0);
0skips the uncertainty and returns the plain point estimate.Default=20000.- method
How the precession constant is converted to Earth-Moon distance, length of day and obliquity (character, passed to
ctest_earthmoon):"angular_momentum"(conservation of Earth-Moon angular momentum) or"astrogeo22"(inversion of the AstroGeo22 curve of Farhat et al., 2022).Default=c("angular_momentum", "astrogeo22"), i.e."angular_momentum".- seed
Seed of the random number generator (integer), so that the Monte Carlo results can be reproduced;
NULLleaves the current random state unchanged.Default=NULL.- data_dir
Folder that contains the data tables
AstroGeo22.txtandLa04gisi.csv(character path).NULLusesgetOption("cocoR.data")or the copies installed with WaverideR.Default=NULL.