import { BaseEstimator, Params } from '../base/estimator';
export interface FeatureUnionProps {
    /** [name, transformer] pairs whose outputs are concatenated column-wise. */
    transformerList: Array<[name: string, transformer: BaseEstimator]>;
}
/** Concatenates the outputs of several transformers, like sklearn's FeatureUnion. */
export declare class FeatureUnion extends BaseEstimator {
    private transformerList;
    constructor(props: FeatureUnionProps);
    getParams(): Params;
    /** Supports nested `name__param` addressing like Pipeline. */
    setParams(params: Params): this;
    getTransformer(name: string): BaseEstimator;
    fit(X: number[][], y?: number[]): void;
    transform(X: number[][]): number[][];
    fitTransform(X: number[][], y?: number[]): number[][];
}
export declare function hstack(blocks: number[][][], nRows: number): number[][];