Estimate slope/intercept of carbon isotope calibration regression

Performs regression between measured and known carbon isotope and mole fractions to generate a transfer function and associated uncertainty estimates using both 5-fold and leave-one-out cross-validation methods. Regression occurs either on 12CO2/13CO2 mole fractions (gainoffset method) or on the CO2 and d13C values (linreg).

Usage

fit_carbon_regression(
  ref_data,
  method,
  calibration_half_width,
  plot_regression_data = FALSE,
  plot_dir = "/dev/null",
  site,
  min_nobs = NA
)

Arguments

ref_data

Reference data.frame from which to estimate calibration parameters.

method

Are we using the gain-and-offset method ("gainoffset"), formerly called the Bowling et al. 2003 method in this package, or direct linear regression of d13C and CO2 mole fractions ("linreg")?

calibration_half_width

Determines the period (in days) from which reference data are selected (period is 2*calibration_half_width).

plot_regression_data

True or false - should we plot the data used in the regression? Useful for debugging.

plot_dir

If plot_regression_data is true, where should the plots be saved?

site

Needed for regression plots.

min_nobs

Minimum number of high-frequency observations to define a peak.

Value

Returns a data.frame of calibration parameters. If method == "gainoffset", then data.frame includes gain and offset parameters for 12CO2 and 13CO2, and r^2 values for each regression. If method == "linreg", then data.frame includes slope, intercept, and r^2 values for d13C and CO2 values.

Author

Rich Fiorella rfiorella@lanl.gov