class PeriodicDummies {

    public Matrix matrix(int len) {
        Matrix m = new Matrix(len, period);
        DataBlockIterator columns = m.columns();
        DataBlock col = columns.getData();
        int pos = 0;
        do {
            int beg=(pos++)-start;
            if (beg<0)
                beg+=period;
            col.extract(beg, -1, period).set(1);
        } while (columns.next());
        return m;
    }

    public  PeriodicDummies(int period);
    public  PeriodicDummies(int period, int start);

}