import { Datum } from '../options';
export interface DataTransitionOptions {
    /** What makes a row the same row across the update; without it rows go by position. */
    key?: string | ((datum: Datum, index: number) => unknown);
    /**
     * Fields the chart reads as values — the ones a bar takes its height from.
     * A row entering starts with these at zero and grows; a row leaving sinks
     * back to zero and is gone. Fields nobody named are set straight away: a
     * category or an x coordinate has no base to grow from.
     */
    valueFields?: readonly string[];
}
/** A frame of an update: the rows to draw, and how much room each of them takes. */
export interface TransitionFrame {
    data: Datum[];
    /**
     * How much of a band each row takes, 0..1, row by row. A row that stayed
     * takes a whole one; one arriving grows into its own, one leaving gives its
     * own up — so the categories around it spread rather than snap.
     */
    weights: number[];
}
/** The frame at factor 0..1; at 1 the new data itself, at full width. */
export type DataTransition = (t: number) => TransitionFrame;
/**
 * The frames between two sets of rows, or nothing when there is no way to draw
 * one: no key to match rows by and a different number of them, or no rows at
 * all on either end.
 */
export declare function planDataTransition(from: readonly Datum[], to: readonly Datum[], options?: DataTransitionOptions): DataTransition | undefined;
/** Linear interpolation of the numeric fields between two rows. */
export declare function lerpDatum(from: Datum, to: Datum, t: number): Datum;