/**
 * Rank correlation metrics for evaluation
 */
/**
 * Spearman's rank correlation coefficient.
 * Measures monotonic relationship between predicted and ground truth rankings.
 *
 * @param predicted - Predicted ranking (array of item IDs in rank order)
 * @param groundTruth - Ground truth ranking (array of item IDs in rank order)
 * @returns ρ ∈ [-1, 1], where 1 = perfect agreement, -1 = perfect disagreement
 */
export declare const spearmanCorrelation: (predicted: string[], groundTruth: string[]) => number;
/**
 * Kendall's tau rank correlation.
 * Counts concordant vs discordant pairs.
 *
 * @param predicted - Predicted ranking
 * @param groundTruth - Ground truth ranking
 * @returns τ ∈ [-1, 1]
 */
export declare const kendallTau: (predicted: string[], groundTruth: string[]) => number;
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