/**
 * Type of a color scale function.
 */
export declare type ColorScale = (value: number) => string;
/**
 * 1-dimensional interval between two numbers.
 */
export declare type Range = [number, number];
/**
 * Creates a color scale.
 * @param  range  Array containing minimum and maximum values.
 * @param  scale  Range of the color scale,
 * @param  invert True if color scale should be inverted.
 * @return        Color scale.
 */
export declare function colorScale(range: Range, scale?: any, invert?: boolean): (value: number) => string;
/**
 * Determines critical points for a gradient depending on a range.
 * @param  range Range of the gradient.
 * @return       Array of critical points in the gradient in order from highest to lowest.
 */
export declare function criticalGradientPoints(range: Range): number[];
/**
 * Creates an interpolation function for values of an array.
 * @param  values Array of values to interpolate between.
 * @return        Interpolation function for values of an array.
 */
export declare function interpolation(values: number[]): (percentage: number) => number;
/**
 * Returns a nicer readable representation of a number.
 * @param  value Input number.
 * @return       Readable representation.
 */
export declare function niceNumber(value: number): string;
/**
 * Creates a normalization function for normalizing between -1 and 1.
 * @param  range Array containing minimum and maximum values.
 * @return       Normalization function for normalizing between -1 and 1.
 */
export declare function normalization(range: Range): (value: number) => number;
/**
 * Determines the minimum and maximum value for an array of arrays of numbers.
 * @param values Array of arrays of numbers.
 * @return
 */
export declare function range(values: number[][]): Range;