Thanks  a lot.

I actually have same imports. I had to modify definitions for Funcs:

private

Func<object, object> _getValue;

private Func<object, object> _getWeight;

as well as specify data type for Cast() method and it runs:

IList dataItems = items.Cast<DataRowMetadata>().Select(drm => drm.DataObject).ToList();

Thanks a lot again,

Alex

If it helps, I am targeting framework 4 and my imports are

using System;

using System.Collections;

using System.Collections.Generic;

using System.Linq;

using Infragistics.Olap;

using Infragistics.Olap.FlatData;

I don't think there are any special libraries

Hi,

I am trying to achieve similar goal for my WA properties and hoped to steal your custom aggregator :-)

Not able to compile it though . Do you use some specific libs for Func and Linq ?

I am having the following comp. time errors :

Error 231 Using the generic type 'System.Func<TResult>' requires 1 type arguments 

Error 236 The call is ambiguous between the following methods or properties: 'Stealth.Components.PivotGrid.Model.DerivedData.IgWeightedAverageAggregator.Evaluate(Infragistics.Olap.IAggregationResult, Infragistics.Olap.IAggregateable, System.Collections.IEnumerable)' and 'Stealth.Components.PivotGrid.Model.DerivedData.IgWeightedAverageAggregator.Evaluate(Infragistics.Olap.IAggregationResult, Infragistics.Olap.IAggregateable, System.Collections.IEnumerable)' 

Error 233 'System.Linq.Queryable.Cast<TResult>(System.Linq.IQueryable)' is a 'method', which is not valid in the given context 

Can you please help me to get your aggreagtor running ?

Thanks a lot in advance,

Alex

This works

public class IgWeightedAverageCache
    {
        /// 

        /// sum(Weight * Value)
        /// 

        private double _numerator = 0;
        /// 

        /// sum(Weight)
        /// 

        private double _denominator = 0;

        internal IgWeightedAverageCache()
        {
        }

        internal IgWeightedAverageCache(double numerator, double denominator)
        {
            _numerator = numerator;
            _denominator = denominator;
        }

        internal  double WeightedAverage
        {
            get
            {
                return _numerator/_denominator;
            }
        }

        public void Add(double weight, double value)
        {
            _numerator += weight*value;
            _denominator += weight;
        }
    }

 public class IgWeightedAverageResult : IAggregationResult
    {
        private readonly IgWeightedAverageCache _cache;

        public IgWeightedAverageResult()
        {
            this._cache = new IgWeightedAverageCache();
        }

        public IgWeightedAverageCache Cache
        {
            get
            {
                return this._cache;
            }
        }

        public double Value
        {
            get
            {
                return this.Cache.WeightedAverage;
            }

            set
            {
                throw new NotImplementedException();
            }
        }

        object IAggregationResult.Value
        {
            get
            {
                return this.Value;
            }
        }

        object IAggregationResult.Cache
        {
            get
            {
                return this.Cache;
            }
        }
    }
/// 

    /// TODO: Flyweight?
    /// 

    public class IgWeightedAverageAggregator :
        IAggregator
    {
         
        private readonly string _valuePropertyName;
        private readonly string _weightPropertyName;
        private Func _getValue;
        private Func _getWeight;
        
        public IgWeightedAverageAggregator(string valuePropName, string weightPropName)
        {
            _valuePropertyName = valuePropName;
            _weightPropertyName = weightPropName;
        }

        public string Identity
        {
            get;
            set;
        }

        private void InitReflection(object item)
        {
            if (_getValue == null)
            {
                lock (this)
                {
                    if (_getValue == null)
                    {
                        Type itemsType = item.GetType();
                        var valuePropertyInfo = itemsType.GetProperty(_valuePropertyName);
                        var weightPropertyInfo = itemsType.GetProperty(_weightPropertyName);
                        _getValue = ReflectionHelper.CreatePropertyGetMethod(valuePropertyInfo);
                        _getWeight = ReflectionHelper.CreatePropertyGetMethod(weightPropertyInfo);
                    }
                }
            }

        }

        public IAggregationResult
            Evaluate(IAggregationResult oldResult,
                     IAggregateable aggregateable,
                     IEnumerable items)
        {
            var result = new IgWeightedAverageResult();

            IList dataItems = items.Cast().Select(drm => drm.DataObject).ToList();

            if (dataItems.Count > 0)
            {
                InitReflection(dataItems[0]);

                foreach (object dataItem in dataItems)
                {
                    var weight = (double?) _getWeight(dataItem);
                    var value = (double?)_getValue(dataItem);

                    if (weight != null && value != null)
                    {
                        result.Cache.Add(weight.Value, value.Value);
                    }
                }
            }
            return result;
        }

        public IAggregationResult
            Evaluate(IAggregationResult oldResult,
                     IAggregateable aggregateable,
                     IEnumerable items)
        {
            return this.Evaluate((oldResult as IgWeightedAverageResult),
                aggregateable, items);
        }

        public IAggregationResult
            Evaluate(IAggregationResult oldResult,
                     double value)
        {
            throw new NotImplementedException();
        }

        public IAggregationResult
            Evaluate(IAggregationResult oldResult, object value)
        {
            throw new NotImplementedException();
        }
    }

I am looking at your examples.  Is it actually possible to do a weighted average?  For example, if I have a Value and Weight columns, the aggregation of Value should be sum(Value[i]*Weight[i])/sum(weight[i])?  Can you give an example of that?