>>So far, so good:

        public static void Main()
>>        {
>>            var result = GetAverage(new int[] {357, 2, 359, 356, 4, 2, 355, 22});  //Result : 2
>>            result = GetAverage(new int[] { 180, 182, 175, 178, 183, 185, 177, 172 });   //Result: 44 :-{
>>        }
>>
>>        public static double GetAverage(int[] values)
>>        {
>>            double c = 0;
>>            double s = 0;
>>
>>            foreach (int i in values)
>>            {
>>                double r = DegreeToRadian(i);
>>                c += Math.Cos(r);
>>                s += Math.Sin(r);
>>            }
>>
>>            double a = Math.Atan2(s, c);
>>
>>            return RadianToDegree(a);
>>        }
>>
>>        public static double DegreeToRadian(double angle)
>>        {
>>            return Math.PI * angle / 180.0;
>>        }
>>
>>        public static double RadianToDegree(double angle)
>>        {
>>            return angle * (180.0 / Math.PI);
>>        }

>> More testing......
>
>
>Took a bit of your code - adding vectors
>To my surprise Atan2() is clever - and returns the right quadrant
>
>

>		public static int GetAverage(IEnumerable<int> readings)
>		{
>			double s = 0.0, c = 0.0;
>			bool haveData = false;
>
>			foreach (int value in readings)
>			{
>				double rads = DegreeToRadian(value);
>				
>				s += Math.Sin(rads);
>				c += Math.Cos(rads);
>				haveData = true;
>			}
>			
>			int result = 0;
>			if (haveData)
>			{
>				double rads;
>
>				if (c == 0)
>				{
>					rads = s >= 0.00 ? Math.PI / 2.0 : -Math.PI / 2.0;
>				}
>				else
>					rads = Math.Atan2(s, c);
>
>				result  = (int)RadianToDegree(rads);
>
>			}
>			return result;
>		}
>		public static double DegreeToRadian(double degrees)
>		{
>			return Math.PI * Modulo(degrees, 360.00) / 180.0;
>		}
>
>		 public static double RadianToDegree(double rads)
>		{
>			return Modulo(rads, Math.PI * 2) * (180.0 / Math.PI);
>		}
>		public static double Modulo(double dividend, double divisor)
>		{
>			return (dividend % divisor)
>					+ (Math.Sign(dividend) * Math.Sign(divisor) >= 0 ? 0 : divisor);
>		}
>

I ended up with this (JScript):

function getAverageAngle(angleArray) {
    var c = 0;
    var s = 0;
    
    for (var i = 0; i < angleArray.length; i++) {
        var r = degreeToRadian(angleArray[i]);
        c += Math.cos(r);
        s += Math.sin(r);
    }
    var a = Math.atan2(s, c);
    var result = radianToDegree(a);
    if (result < 0)
        result = 360 + result;
    return result;
}

function degreeToRadian(angle) {
    return Math.PI * angle / 180;
}

function radianToDegree(angle) {
    return angle * (180 / Math.PI);
}

Raw and average seem to tally.