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Evaluates the robustness of a hydrological model performance metric (e.g., Bias) with respect to an explanatory variable (e.g., discharge characteristics), using a Spearman correlation test. The function returns a Boolean indicating whether a significant correlation exists, implying potential lack of robustness.

Based on the RAT (Robustness Assessment Test) methodology introduced by Nicolle et al. (2020), this function tests whether the variability of a model performance criterion can be explained by an explanatory variable, suggesting a lack of robustness if so.

Usage

compute_RAT_X(Bias, X, thresh = 0.05)

Arguments

Bias

Numeric vector of model performance scores (e.g., Bias) across sub-basins, time periods, or experiments.

X

Numeric vector of an explanatory variable (e.g., flow regime characteristic) of the same length as Bias.

thresh

Numeric threshold for the p-value of the Spearman correlation test. Default is 0.05 (5% significance level).

Value

Logical. Returns TRUE if the correlation is significant (i.e., p-value < thresh), indicating a lack of robustness; FALSE otherwise.

References

Nicolle, P., Andréassian, V., Royer-Gaspard, P., Perrin, C., Thirel, G., Coron, L., & Santos, L. (2020). RAT – a robustness assessment test for calibrated and uncalibrated hydrological models. Hydrological Sciences Journal, 65(6), 959–972. https://doi.org/10.1080/02626667.2020.1737689