public NumericIndicator previous(int barCount) {
        return NumericIndicator.of(new PreviousValueIndicator(this, barCount));
    }
@Test
    public void previous() {
        final NumericIndicator numericIndicator = NumericIndicator.of(cp1);
        final Indicator<Num> previous = numericIndicator.previous();
        assertNumEquals(cp1.getValue(0), previous.getValue(1));

        final Indicator<Num> previous3 = numericIndicator.previous(3);
        assertNumEquals(cp1.getValue(3), previous3.getValue(6));
    }