public void testRowCount() {
        DefaultKeyedValues2D d = new DefaultKeyedValues2D();
        assertEquals(0, d.getRowCount());
        d.addValue(new Double(1.0), "R1", "C1");
        assertEquals(1, d.getRowCount());
        d.addValue(new Double(2.0), "R2", "C1");
        assertEquals(2, d.getRowCount());