### Question:
SigmaIndicator extends SingleValueCalculationIndicator { public SigmaIndicator(int length, TimeInterval interval) { this(length, interval, null); } SigmaIndicator(int length, TimeInterval interval);  SigmaIndicator(int length, TimeInterval interval, ToDoubleFunction<Candle> valueGetter);   }### Answer:
@Test public void sigmaIndicator() { int i = 0; SigmaIndicator indicator = new SigmaIndicator(5, TimeInterval.MINUTE); indicator.accumulate(CandleHelper.newCandle(i, values[i++])); indicator.accumulate(CandleHelper.newCandle(i, values[i++])); assertEquals(1, indicator.getValue(), 0.0001); indicator.accumulate(CandleHelper.newCandle(i, values[i++])); assertEquals(1.224744871391589, indicator.getValue(), 0.0001); indicator.accumulate(CandleHelper.newCandle(i, values[i++])); assertEquals(1.34164078649987387, indicator.getValue(), 0.0001); indicator.accumulate(CandleHelper.newCandle(i, values[i++])); assertEquals(1.414213562373095, indicator.getValue(), 0.0001); indicator.accumulate(CandleHelper.newCandle(i, values[i++])); assertEquals(1.414213562373095, indicator.getValue(), 0.0001); }