Unable to calculate WilderMovingAverage

Hi,

I`m trying to calculate ATR using Wilder Moving Average. Here is my code:

var atr = new WilderMovingAverage()
{
	Length = 2,
};

foreach (var candle in candles.Take(10))
{
	atr.Process(candle);
}

var result = atr.GetValue(0);

The result is always 0, no matter what index I will select.