Opc.Ua.Server.StdDevAggregateCalculator.ComputeStdDev C# (CSharp) Method

        protected DataValue ComputeStdDev(TimeSlice slice, bool includeBounds, int valueType)
        {
            // get the values in the slice.
            List<DataValue> values = null;

            if (includeBounds)
            {
                values = GetValuesWithSimpleBounds(slice);
            }
            else
            {
                values = GetValues(slice);
            }

            // check for empty slice.
            if (values == null || values.Count == 0)
            {
                return GetNoDataValue(slice);
            }

            // get the regions.
            List<SubRegion> regions = GetRegionsInValueSet(values, false, true);

            List<double> xData = new List<double>();
            double average = 0;
            bool nonGoodDataExists = false;

            for (int ii = 0; ii < regions.Count; ii++)
            {
                if (StatusCode.IsGood(regions[ii].StatusCode))
                {
                    xData.Add(regions[ii].StartValue);
                    average += regions[ii].StartValue;
                }
                else
                {
                    nonGoodDataExists = true;
                }
            }

            // check if no good data.
            if (xData.Count == 0)
            {
                return GetNoDataValue(slice);
            }

            average /= xData.Count;

            // calculate variance.
            double variance = 0;

            for (int ii = 0; ii < xData.Count; ii++)
            {
                double error = xData[ii] - average;
                variance += error*error;
            }

            // use the sample variance if bounds are included.
            if (includeBounds)
            {
                variance /= (xData.Count + 1);
            }
            
           // use the population variance if bounds are not included.
            else
            {
                variance /= xData.Count;
            }

            // select the result.
            double result = 0;

            switch (valueType)
            {
                case 1: { result = Math.Sqrt(variance); break; }
                case 2: { result = variance; break; }
            }

            // set the timestamp and status.
            DataValue value = new DataValue();
            value.WrappedValue = new Variant(result, TypeInfo.Scalars.Double);
            value.SourceTimestamp = GetTimestamp(slice);
            value.ServerTimestamp = GetTimestamp(slice);

            if (nonGoodDataExists)
            {
                value.StatusCode = StatusCodes.UncertainDataSubNormal;
            }

            value.StatusCode = value.StatusCode.SetAggregateBits(AggregateBits.Calculated);

            // return result.
            return value;
        }
        #endregion