/**
 * True Range (TR).
 * TR[i] = max(high[i]-low[i], |high[i]-close[i-1]|, |low[i]-close[i-1]|).
 * Preserves NaNs and returns NaN where inputs are invalid.
 * @param high High price series
 * @param low Low price series
 * @param close Close price series
 * @returns Float64Array of TR values
 */
export declare function tr(high: ArrayLike<number>, low: ArrayLike<number>, close: ArrayLike<number>): Float64Array;
/**
 * Average True Range (ATR).
 * Computes ATR using Wilder's RMA over the true-range series. Handles NaNs
 * via the `rma` NaN-aware implementation; returns NaN for indices before the
 * lookback is filled.
 * @param high High price series
 * @param low Low price series
 * @param close Close price series
 * @param period Lookback period (must be > 0)
 * @returns Float64Array of ATR values
 */
export declare function atr(high: ArrayLike<number>, low: ArrayLike<number>, close: ArrayLike<number>, period: number): Float64Array;
export declare function natr(high: ArrayLike<number>, low: ArrayLike<number>, close: ArrayLike<number>, period: number): Float64Array;