How to filter List<T> and find average to make a distinct List<T>

Question

How can I filter a list into distinct values by a specific field and where the values weren't distinct take their averages. Please see example

{
Public int Time;
Public float Voltage;
Public float Current;
Public Resistance(int time, float voltage, float current)
{
Time = time;
Voltage = voltage;
Current = current;
}
Public List<Resistance> _resistances = new List<Resistance>();
_resistances.Add(new Resistance(Time = 1, Voltage =3.2, Current = 1);
_resistances.Add(new Resistance(Time = 1, Voltage =4.0, Current = 2);
_resistances.Add(new Resistance(Time = 1, Voltage =6.5, Current = 6);
_resistances.Add(new Resistance(Time = 2, Voltage =3.2, Current =4);
_resistances.Add(new Resistance(Time =2, Voltage =3.2, Current = 2);
_resistances.Add(new Resistance(Time = 3, Voltage 5, Current = 1);

Aim is to have a list with:

_resistance[0]{ Time =1,, Voltage = Average(3.2,4,6.5), Current = Average(1,2,6))
_resistance[1]{ Time =2,, Voltage = Average(3.2,3.2,5), Current = Average(4,2,1))
}

For any arbitrary values and quantity of entries

I have tried the following

            int divisor = 1;
            double voltageSum = 0;
            double currentSum = 0;

            while (j >= 1)
            {
                while (_resistances[j].Time== _resistances[j - 1].Time)
                {
                    divisor++;
                    voltageSum += _resistances[j].Voltage;
                    currrentSum += _resistances[j].Current;
                    _resistances.RemoveAt(j);
                    j -= 1;
                }

                var averageVoltage = voltageSum / divisor;
                var averageCurrent = currentSum / divisor;
                _rawDataList[j].Voltage = (float)averageVoltage;
                _rawDataList[j].Current= (float)averageCurrent;
                j -= 1;
            }

I know this is wrong but I cant seem to figure out the logic to modifying a list, I think creating a new list and appending in a forloop maybe the way forward but I cant work it out. I think Linq may help, but not too experienced with Lambda expressions. Thanks in advance

Answer 1

You can accomplish this using Linq, group your records by Time and use the Average function to compute the values for Voltage and Current for the Time groups:

_resistances
 .GroupBy(r => r.Time)
 .Select(g => new { 
      Time = g.Key, 
      Voltage = g.Average(r => r.Voltage), 
      Current = g.Average(r => r.Current) 
 });