Get Average Using Linq

Get Average Using LINQ

Are you looking for an average rating per user id? If so, then you need to use both GroupBy and Average.

var rates = ctx.Rates
               .Where( r => r.Id == Id )
               .GroupBy( g => g.UserId, r => r.Rating )
               .Select( g => new
                {
                   UserId = g.Key,
                   Rating = g.Average()
                });

How can I get the average of a property in a list using LINQ?

Try something like that;

var avg = btnCountViewsList.Where(x => x.Month == 5).Select(x => x.Views).DefaultIfEmpty(0).Average();

Also I suggest you to use DefaultIfEmpty for possible empty sets. Otherwise if btnCountViewsList is empty, an exception is throwed.

How to use linq to calculate average from grouped data where value 0 using let

you need to average field 3 after the filter

 let field3Average = dg.Where(g => g.field3 > 0.0).Average(g => g.field3)

Finding the max of average in linq

Using Linq "query syntax"

var best = from student in students
           group student by student.Id into studentAverage
           let average = studentAverage.Average (s => s.Marks)
           orderby average descending
           select new { id = studentAverage.Key, average };
           // change projection to have only id or average

Using Linq "method syntax"

var best =
    students
    .GroupBy (student => student.Id,
              student => student.Marks,
              (id, marks) => new { id, average = marks.Average () })
    .OrderByDescending (studentAverage => studentAverage.average)
    // add a projection (Select) here to have only id or average
    .FirstOrDefault ();

Maybe simpler alternative but more oriented toward getting only the Id

var best =
    students
    .ToLookup (s => s.Id, s => s.Marks)
    .OrderByDescending (marksById => marksById.Average ())
    .FirstOrDefault ();

// Key will contain the Id but Average must be calculated again
// var avg = best.Average();

Using "classic" code (longer, but clearer steps)

var studentMarks = new Dictionary<int, List<double>> (students.Count);

foreach (var student in students)
{
    int id = student.Id;
    List<double> marks;

    if (!studentMarks.TryGetValue (id, out marks))
    {
        marks = new List<double> ();
        studentMarks.Add (id, marks);
    }

    marks.Add (student.Marks);
}

double? bestAverage = null;
int? idOfBest = null;

foreach (var idAndMarks in studentMarks)
{
    var average = 0.0;

    foreach (var mark in idAndMarks.Value)
    {
        average += mark;
    }

    average /= idAndMarks.Value.Count;

    if (average > bestAverage)
    {
        bestAverage = average;
        idOfBest = idAndMarks.Key;
    }
}

Conditional average using linq from qrouped data returns nothing

It sounds like there are groups that don't have any items that satisfy the Where condition. The Average of an empty sequence of non-nullable values is not zero - it is an exception. For example, there are no items for Field1 as 6 that have Field3 greater than zero.

I notice in your "What I want" table you only have the values with Field1 as 3 - if this represents your real scenario, maybe filter the second table.

A possible fix is to project the values to be nullable:

let AverageField3 = dg.Where(g => g.Field3 > 0.0).Average(g => (int?)g.Field3)

this will give a null value when there aren't any inputs. If you want zero:

let AverageField3 = dg.Where(g => g.Field3 > 0.0)
                      .Average(g => (int?)g.Field3)
                      .GetValueOrDefault();

(replace the int? with float? or decimal? or whatever it is that matches your data)

How to get average of list within lists using linq?

I have tested the solution I put in the update:

double average = busInCat.Max(b=> b.GetReviews().Average(r => r.getRateing()));
return busInCat.Where(b => b.GetReviews().Average(r => r.getRateing()) == average).T

The above code does indeed work as intended.

How to get Average of grouped results in Linq query

In the original query you probably want to do this.

//other code removed for brevity
select new {
    Date = key,
    Rating = g.Count() > 0 ? g.Average(x => x.Rating) : 0
};

And then return the result

return Json(ratingsByMonth);

how to calculate average for each item in a list with LINQ?

I'm a bit short on time to test it but I think it should work with a few small tweaks. If I've made any typos, let me know:

var listadoA = alumnos.GroupJoin(examenes, 
                    a => a._id,
                    e => e._alumnoId,
                    (a, eGroup) => new
                    {
                        Alumno = a,
                        Examenes = eGroup
                        
                    }).Where(p => p.Examenes.Count() >= 1).OrderBy(p => p.Alumno._nombre).ToList();
foreach (var obj in listadoA){
        var promedio = obj.Examenes.Average(e => e._nota);

I'm curious why your fields starting with underscore are publicly accessible; that's the naming convention for a private field.. should really have public properties for them. Also, I've assumed that "nota" is the exam score..

Join and Calculate Average of column using LINQ to sql

var query = from video in Video join 
    comment in Comment on comment.VideoId equals video.VideoId;

Console.WriteLine("Average Rating: " + query
    .Where(i => i.VideoName = videoName)
    .Average(i => i.Rating));

Get Average Using Linq