/**
 * Size scales for proportional symbols and line widths.
 *
 * The default is `sqrt`, and that default is a correctness decision rather than a
 * preference. Readers judge a circle by its **area**, so mapping value linearly
 * to radius makes area grow with the square of the value: a country with ten
 * times the population gets a hundred times the ink. Square-root scaling makes
 * area proportional to value, which is the only encoding that reads honestly.
 *
 * `linear` is available because line widths and some designs genuinely want it,
 * and it warns in dev mode when used for symbol radii.
 *
 * @module scales/SizeScale
 */
import type { SizeLegendEntry, SizeOptions, SizeScaleType } from '../types';
export declare class SizeScale {
    readonly type: SizeScaleType;
    readonly domain: [number, number];
    readonly range: [number, number];
    readonly warnings: string[];
    constructor(values: readonly (number | null | undefined)[], options?: SizeOptions);
    /** Normalised position of a value within the domain, 0..1. */
    private position;
    /** Radius in screen pixels. Returns null for values that cannot be sized. */
    radius(value: unknown): number | null;
    /**
     * Reference sizes for a nested-circle legend.
     *
     * Three circles at round values, drawn concentrically, is the only bubble legend
     * that lets a reader actually decode areas. Datawrapper does this well and
     * almost nobody else ships it at all.
     */
    legendEntries(count?: number, format?: (v: number) => string): SizeLegendEntry[];
}
export declare function createSizeScale(values: readonly (number | null | undefined)[], options?: SizeOptions): SizeScale;
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