/** A dense numeric feature matrix, indexed as [sample][feature]. */
export type DenseMatrix = number[][];
/** Numeric input accepted by sparse-aware estimators. */
export type NumericMatrix = DenseMatrix | CSRMatrix;
/** Raw text documents accepted by text transformers. */
export type TextDocuments = string[];
/** Data that may flow between Pipeline steps. */
export type FeatureData = NumericMatrix | TextDocuments;
export type FeatureDataKind = 'dense' | 'csr' | 'text';
/**
 * Minimal compressed-sparse-row matrix for browser and Node.js workloads.
 *
 * The three backing arrays use the conventional CSR layout: values and their
 * column indices are grouped by row, while indptr stores the start offset for
 * every row (plus one final sentinel). Zero values are not stored.
 */
export declare class CSRMatrix {
    private dataState;
    private indicesState;
    private indptrState;
    readonly nRows: number;
    readonly nCols: number;
    constructor(data: number[], indices: number[], indptr: number[], shape: [number, number]);
    get shape(): [number, number];
    get nnz(): number;
    /** Defensive copies keep callers from invalidating the CSR layout. */
    get data(): readonly number[];
    get indices(): readonly number[];
    get indptr(): readonly number[];
    static fromDense(matrix: DenseMatrix): CSRMatrix;
    get(row: number, column: number): number;
    row(row: number): number[];
    forEachNonZeroInRow(row: number, callback: (column: number, value: number) => void): void;
    selectRows(rows: number[]): CSRMatrix;
    toDense(): DenseMatrix;
    private assertRow;
}
export declare function isCSRMatrix(value: unknown): value is CSRMatrix;
export declare function matrixShape(X: NumericMatrix): [number, number];
export declare function matrixRow(X: NumericMatrix, row: number): number[];
export declare function forEachNonZeroInRow(X: NumericMatrix, row: number, callback: (column: number, value: number) => void): void;