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Compute Hollstein-style t-values between all series in two rwl-style data frames

Source: R/trs_tho.R
trs_tho.Rd

This function calculates Hollstein (1980) t-values for all pairwise comparisons between tree-ring series in two data frames, using log-transformed growth ratios. The method computes year-to-year growth ratios and applies correlation-based t-statistics for crossdating analysis.

Usage

trs_tho(x, y = NULL, min_overlap = 50, as_df = FALSE, transform = TRUE)

Arguments

x

A data frame of test tree-ring series in rwl format (years as rownames, series as columns). All columns must be numeric.

y

A data frame of reference tree-ring series in rwl format. If NULL, uses x for self-comparison. Default is NULL.

min_overlap

Integer. Minimum number of overlapping years required between series pairs to compute t-values. Must be >= 3. Default is 50.

as_df

Logical. If TRUE, returns results in long-format data frame. If FALSE, returns list of matrices. Default is FALSE.

transform

Logical. If TRUE, applies Hollstein transformation (log growth ratios). If FALSE, assumes input data is already transformed. Default is TRUE.

Value

Depending on as_df parameter:

  • If as_df = FALSE (default): A list containing:

    • t_Ho: Matrix of Hollstein t-values with test series as rows, reference series as columns

    • overlap: Matrix of overlap counts (number of common years) with same dimensions

  • If as_df = TRUE: A data frame with columns:

    • series: Name of test series

    • reference: Name of reference series

    • t_Ho: Hollstein t-value

    • overlap: Number of overlapping years

Details

The Hollstein method involves:

  1. Alignment of series by common years

  2. Computation of log-transformed growth ratios: \(100 \times \log_{10}(x_t / x_{t-1})\)

  3. Calculation of Pearson correlation between transformed series

  4. Computation of t-statistic: \(t = r \sqrt{n-3} / \sqrt{1-r^2}\)

Where \(n\) is the number of overlapping observations (original years, not growth ratios). The degrees of freedom are adjusted by subtracting 3 to account for the growth ratio transformation.

Negative correlations are set to 0, and perfect correlations (|r| ≥ 1) result in infinite t-values to handle floating-point precision issues.

References

Hollstein, E. (1980). Mitteleuropäische Eichenchronologie. Verlag Philipp von Zabern, Mainz.

See also

trs_tbp for Baillie & Pilcher t-values

Examples

if (FALSE) { # \dontrun{
# Create sample data
rwl_test <- trs_pseudo_rwl(n_series = 3, series_length = 100, end_date = 2020)
rwl_ref <- trs_pseudo_rwl(n_series = 2, series_length = 80, end_date = 2015)

# Compute Hollstein t-values (matrix format)
result <- trs_tho(rwl_test, rwl_ref, min_overlap = 30)
print(result$t_Ho)
print(result$overlap)

# Compute t-values (data frame format)
result_df <- trs_tho(rwl_test, rwl_ref, min_overlap = 30, as_df = TRUE)
print(result_df)

# Self-comparison within single dataset
self_comparison <- trs_tho(rwl_test, min_overlap = 40)
} # }