R/identifiability_functions.R
assess_calib_curve_equif.RdAssess the equifinality or time spans in the input radiocarbon calibration curve
assess_calib_curve_equif(calib_df, equi_list = NA)
| calib_df | The calibration data frame, with columns year_BP, uncal_year_BP, and uncal_year_BP_error |
|---|---|
| equi_list | (Optional) The result of a call to calc_calib_curve_equif_dates |
A list of with named variables can_invert and inv_span_list (see details)
The input calibration data frame has three columns: year_BP, uncal_year_BP, and uncal_year_BP_error. A time span is equifinal if, for each date in the span, there is at least one other date in the radiocarbon calibration curve with the same fraction modern value. Conversely, a time span is not equifinal if this is not true (all dates in the time span correspond to a unique fraction modern value). Thus, the calibration curve is divided into alternating equifinal and non-equifinal spans. This function identifies these regions for the input calibration data frame, calib_df.
Although calib_df uses year BP, all calculations and returned data use AD.
A list is returned with two named variables: can_invert and inv_span_list (inv = invert, which is conceptually identical to non-equifinal).
can_invert is a boolean that indicates whether each entry (row) in the calibration data frame, calib_df, is inside or outside an invertible region.
inv_span_list is a list summarizing information about all the invertible (non-equifinal) time spans. It contains the following named variables:
ind -- Indices (rows) of calib_df following within the invertible time span tau_left -- Calendar date (AD) of the left (earlier) boundary of the invertible time span phi_left -- Fraction modern value of the left (earlier) boundary of the invertible time span tau_right -- Calendar date (AD) of the right (later) boundary of the invertible time span phi_right -- Fraction modern value of the right (later) boundary of the invertible time span ii_prev -- The index (row) of the calib_df earlier than the invertible region with closest fraction modern value ii_next -- The index (row) of the calib_df later than the invertible region with closest fraction modern value