/**
 * This is the internal implementation of quantiles: when you know
 * that the order is sorted, you don't need to re-sort it, and the computations
 * are faster.
 *
 * @param {Array<number>} x sample of one or more data points
 * @param {number} p desired quantile: a number between 0 to 1, inclusive
 * @returns {number} quantile value
 * @throws {Error} if p ix outside of the range from 0 to 1
 * @throws {Error} if x is empty
 * @example
 * quantileSorted([3, 6, 7, 8, 8, 9, 10, 13, 15, 16, 20], 0.5); // => 9
 */
export declare function quantileSorted(x: number[], p: number): number;
/**
 * 交换数组位置
 * @param arr T[]
 * @param i number
 * @param j number
 */
export declare function swap<T = any>(arr: T[], i: number, j: number): void;
/**
 * Rearrange items in `arr` so that all items in `[left, k]` range are the smallest.
 * The `k`-th element will have the `(k - left + 1)`-th smallest value in `[left, right]`.
 *
 * Implements Floyd-Rivest selection algorithm https://en.wikipedia.org/wiki/Floyd-Rivest_algorithm
 *
 * @param {Array<number>} arr input array
 * @param {number} k pivot index
 * @param {number} [left] left index
 * @param {number} [right] right index
 * @returns {void} mutates input array
 * @example
 * var arr = [65, 28, 59, 33, 21, 56, 22, 95, 50, 12, 90, 53, 28, 77, 39];
 * quickselect(arr, 8);
 * // = [39, 28, 28, 33, 21, 12, 22, 50, 53, 56, 59, 65, 90, 77, 95]
 */
export declare function quickselect(arr: number[], k: any, left?: number, right?: number): void;
/**
 * The [quantile](https://en.wikipedia.org/wiki/Quantile):
 * this is a population quantile, since we assume to know the entire
 * dataset in this library. This is an implementation of the
 * [Quantiles of a Population](http://en.wikipedia.org/wiki/Quantile#Quantiles_of_a_population)
 * algorithm from wikipedia.
 *
 * Sample is a one-dimensional array of numbers,
 * and p is either a decimal number from 0 to 1 or an array of decimal
 * numbers from 0 to 1.
 * In terms of a k/q quantile, p = k/q - it's just dealing with fractions or dealing
 * with decimal values.
 * When p is an array, the result of the function is also an array containing the appropriate
 * quantiles in input order
 *
 * @param {Array<number>} x sample of one or more numbers
 * @param {Array<number> | number} p the desired quantile, as a number between 0 and 1
 * @returns {number} quantile
 * @example
 * quantile([3, 6, 7, 8, 8, 9, 10, 13, 15, 16, 20], 0.5); // => 9
 */
declare function quantile(x: number[], p: number): number;
declare function quantile(x: number[], p: number[]): number[];
export { quantile };