import { StackSegment } from '../kernel';
import { Datum } from '../options';
export declare function numericValues(data: Datum[], key: string): number[];
export declare function uniqueValues(data: Datum[], key: string): unknown[];
export interface StackSeriesDef {
    id: string;
    key: string;
    stackGroup: string;
    /** Normalizes the stack total to this value (e.g. 100 — percentage stack). */
    normalizedTo?: number;
}
/**
 * Cumulative stacking: for each series — y0/y1 arrays by data index.
 * Positive and negative values accumulate separately (diverging stack).
 * With normalizedTo, each category's total is scaled to the given value
 * (positive part — to +normalizedTo, negative — to −normalizedTo).
 */
export declare function computeStacks(data: Datum[], defs: StackSeriesDef[]): Map<string, StackSegment>;