LINQ aggregate and group by periods of time

Question

I\'m trying to understand how LINQ can be used to group data by intervals of time; and then ideally aggregate each group.

Finding numerous examples with explicit dat

Answer 1

A generalised solution:

    static IEnumerable> GroupBy(this IOrderedEnumerable enumerable, TimeSpan timeSpan, Func predicate)
    {
        Grouping grouping = null;
        foreach (var (a, dt) in from b in enumerable select (b, predicate.Invoke(b)))
        {
            if (grouping == null || dt > grouping.Key.End)
                yield return grouping = new Grouping(new DateRange(dt, dt + timeSpan), a);
            else
                grouping.Add(a);
        }
    }

    class Grouping : IGrouping
    {

        readonly List elements = new List();

        public DateRange Key { get; }

        public Grouping(DateRange key) => Key = key;

        public Grouping(DateRange key, T element) : this(key) => Add(element);

        public void Add(T element) => elements.Add(element);

        public IEnumerator GetEnumerator()=> this.elements.GetEnumerator();

        IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
    }

    class DateRange
    {
    
        public DateRange(DateTime start, DateTime end)
        {
            this.Start = start;
            this.End = end;
        }

        public DateTime Start { get; set; }
        public DateTime End { get; set; }
    }

Test based on question (using AutoFixture library)

     void Test()
    {
        var many = new Fixture().CreateMany(100);

        var groups = many.OrderBy(a => a.timestamp).GroupBy(TimeSpan.FromDays(365), a => a.timestamp).Select(a => a.Average(b => b.value)).ToArray();

    }

    public class Sample
    {
        public DateTime timestamp;
        public double value;
    }