class DifferenceStationaryModelHelper {

    public static Matrix aggregation(final int len, final int nagg) {
        int nc = len, nr = nc / nagg;
        Matrix J = new Matrix(nr, nc);
        for (int r = 0, c = 0; r < nr; ++r) {
            for (int k = 0; k < nagg; ++k, ++c) {
                J.set(r, c, 1);
            }
        }
        return J;
    }

    public  DifferenceStationaryModelHelper(final DataBlock y, final Matrix X, final Matrix transformation, final BackFilter difference);
    public  DifferenceStationaryModelHelper(final IModelProvider provider);

}