Astronomical parameters from spectral peaks — astro_from

Wraps ctest() and ctest_earthmoon(): give the wavelength ranges (m) of the cycles you identified in a depth-domain spectrum and an approximate age, and get back the secular frequencies g2-g5 and s3, the precession constant k, the Earth-Moon distance and the length of day, with uncertainties.

Usage

astro_from_peaks(
  age,
  e405,
  e125,
  e95,
  obl = NULL,
  prec_long = NULL,
  prec_mid = NULL,
  prec_short = NULL,
  age_tol = 5,
  nsim = 2000,
  ptest = c(10000, 28000),
  mode = c("auto", "PT", "T", "P"),
  sampleorb = "U",
  method = c("angular_momentum", "astrogeo22"),
  s3_uncertainty = c("published", "scaled"),
  seed = NULL,
  verbose = TRUE,
  data_dir = NULL
)

Arguments

age: Approximate age of the record in Ma (numeric): c(min, max), or a single value, which is widened by age_tol Ma on either side. Required, no default.
e405, e125, e95: Wavelength ranges in metres of the 405-kyr, ~125-kyr and ~95-kyr eccentricity cycles identified in the depth-domain spectrum (each a numeric vector c(min, max)). All three are required, no default.
obl: Wavelength range in metres of the obliquity cycle (k+s3), if identified (numeric vector c(min, max)); NULL if not identified. Default=NULL.
prec_long, prec_mid, prec_short: Wavelength ranges in metres of the precession cycles, from longest to shortest (k+g5; k+g2; k+g4/k+g3), each a numeric vector c(min, max) or NULL. All three must be given for the precession test to be used. Default=NULL.
age_tol: Half-width in Ma of the age range used when age is a single value (numeric, >= 0). Default=5.
nsim: Number of accepted Monte Carlo samples to collect (integer, > 0); passed to ctest. Default=2000.
ptest: Range of precession constants k to sample, in years (numeric vector c(min, max)); passed to ctest. Default=c(10000, 28000).
mode: Which cycles are used in the consistency test (character): "auto" picks the mode from the cycles supplied, "PT" precession and obliquity (tilt), "T" obliquity only, "P" precession only. Passed to ctest. Default=c("auto", "PT", "T", "P"), i.e. "auto".
sampleorb: How the secular frequencies g2-g5 are sampled, passed to ctest (character): "U" uniform within 2 sigma (as in the paper) or "N" normal. Default="U".
method: How the sampled precession constants are converted into an Earth-Moon state (distance, length of day) by ctest_earthmoon (character): "angular_momentum" (Earth-Moon angular-momentum conservation) or "astrogeo22" (inversion of the AstroGeo22 curve). Default=c("angular_momentum", "astrogeo22"), i.e. "angular_momentum".
s3_uncertainty: How the uncertainty of s3 is sampled, passed to ctest (character): "published" follows the published CTest code, in which the relative uncertainty is applied as an absolute one in years (s3 is effectively fixed; use it to reproduce the paper); "scaled" applies it relative to the s3 period, as for g2-g5, giving s3 a realistic spread. Default=c("published", "scaled"), i.e. "published".
seed: Seed of the random number generator (integer), passed to ctest so that the Monte Carlo results can be reproduced; NULL leaves the current random state unchanged. Default=NULL.
verbose: Print progress messages of the Monte Carlo sampling (logical, TRUE or FALSE). Default=TRUE.
data_dir: Folder that contains the AstroGeo22 table AstroGeo22.txt (character path); NULL uses the copy installed with the package. Passed to ctest_earthmoon and astrogeo22. Default=NULL.

Value

object of class `astro_from_peaks`: `$frequencies` (g, s, k in both arcsec/yr and yr), `$earthmoon` (distance, day length, months, days per year), `$periods` (the astronomical periods implied), `$reference` (the AstroGeo22 model at the same age) and the underlying `$ctest`