I have a table with data similar to below:
Group TimePoint Value
1 0 1
1 0 2
1 0 3
1 1 3
1 1 5
I want to project a table as such:
Group TimePoint AverageValue
1 0 2
1 1 4
EDIT: The data is in a datatable.
Anybody any ideas how this can be done with LINQ or otherwise?
Thanks.
You need to perform Group By
The linq you need is something like:
var query = from item in inputTable
group item by new { Group = item.Group, TimePoint = item.TimePoint } into grouped
select new
{
Group = grouped.Key.Group,
TimePoint = grouped.Key.TimePoint,
AverageValue = grouped.Average(x => x.Value)
} ;
For more Linq samples, I highly recommend the 101 Linq samples page - http://msdn.microsoft.com/en-us/vcsharp/aa336747#avgGrouped
Here's a more function-oriented approach (the way I prefer it). The first line won't compile, so fill it in with your data instead.
var items = new[] { new { Group = 1, TimePoint = 0, Value = 1} ... };
var answer = items.GroupBy(x => new { TimePoint = x.TimePoint, Group = x.Group })
.Select(x => new {
Group = x.Key.Group,
TimePoint = x.Key.TimePoint,
AverageValue = x.Average(y => y.Value),
}
);
You can do:
IEnumerable<MyClass> table = ...
var query = from item in table
group item by new { item.Group, item.TimePoint } into g
select new
{
g.Key.Group,
g.Key.TimePoint,
AverageValue = g.Average(i => i.Value)
};
Assuming a class like this:
public class Record
{
public int Group {get;set;}
public int TimePoint {get;set;}
public int Value {get;set;}
}
var groupAverage = from r in records
group r by new { r.Group, r.TimePoint } into groups
select new
{
Group = groups.Key.Group,
TimePoint = groups.Key.TimePoint,
AverageValue = groups.Average(rec => rec.Value)
};
Related
I have a LogData List and which is designed like below.
public class LogDataEntity
{
public string IndexPattern;
public int Type;
public LogDataEntity(string pattern , int type)
{
IndexPattern = pattern;
Type = type;
}
}
List<LogDataEntity> list = new List<LogDataEntity>();
list.add(new LogDataEntity("1,2,9,10", 2));
list.add(new LogDataEntity("1,10", 1));
list.add(new LogDataEntity("1,2,3", 2));
list.add(new LogDataEntity("3,9,10", 3));
list.add(new LogDataEntity("9,10", 2));
list.add(new LogDataEntity("9,10", 2));
And i want the result like below.
[Index] [Type] [Count]
10 : 2 3
9 : 2 3
1 : 2 2
3 : 1 2
2 : 2 2
3 : 3 1
9 : 3 1
10 : 3 1
1 : 1 1
I want to group by and count not only splited string(indexpattern) but also
type too. And i want to count and show them by OrderByDescending(Count).
I think There is multiple group by.
How should i do this with Linq?
You can use SelectMany to create list of (Index, Type) pairs, then group by and count to do the rest:
var pairs = data.SelectMany(x => x.IndexPattern
.Split(",")
.Select(y => new {Index = y, Type = x.Type});
var res = from p in pairs
group p by new { p.Index, p.Type } into grp
select new {
Index = grp.Key.Index,
grp.Key.Type,
grp.Count()
};
(An order by clause can be added before the final Select as required.)
You've, probably, stuck in SelectMany; all the other commands are quite evident:
var result = list
.SelectMany(record => record
.IndexPattern
.Split(',')
.Select(item => {
index = item,
type = record.Type,
}))
.GroupBy(item => item)
.OrderByDescending(chunk => chunk.Count())
.Select(chunk => $"{chunk.index,-10} : {chunk.type,-10} {chunk.Count()}");
Console.WriteLine(string.Join(Environment.NewLine, result));
This is improve version or previous answers.
var pairs = Logs.SelectMany(x => x.IndexPattern.Split(',').Select(y => new {
Index = y, Type= x.Type }));
var pairs2 = (from p in pairs group p by p into grp select new { Index =
grp.Key.Index, Reason = grp.Key.Type, Count = grp.Count() }
).OrderByDescending(p => p.Count);
foreach (var i in pairs2)
{
//print with i
}
I am trying to achieve ranking functionality as below:
Name Points rank
ram 9 1
kamal 9 1
preet 8 2
lucky 7 3
kishan 6.5 4
devansh 6 5
neha 6 5
I have used below code to achieve this:
finalResult = finalResult.OrderByDescending(i => i.points).ThenBy(i => i.academy).ToList();
finalResult = finalResult.AsEnumerable() // Client-side from here on
.Select((player, index) => new RankingEntity()
{
competitorid = player.competitorid,
firstname = player.firstname,
lastname = player.lastname,
academy = player.academy,
points = player.points,
place = player.place,
eventId = player.eventId,
eventname = player.eventname,
categoryname = player.categoryname,
Rank = index + 1
}).ToList();
var t = (from i in finalResult
let rank = finalResult.First(x => x.points == i.points)
select new
{
Col1 = i,
Rank = rank.Rank
}).ToList();
List<RankingEntity> ttt = new List<RankingEntity>();
foreach (var item in t)
{
var a = item.Col1;
var row = new RankingEntity();
row.competitorid = a.competitorid;
row.firstname = a.firstname;
row.lastname = a.lastname;
row.academy = a.academy;
row.points = a.points;
row.place = a.place;
row.eventId = a.eventId;
row.eventname = a.eventname;
row.categoryname = a.categoryname;
row.Rank = item.Rank;
ttt.Add(row);
}
And i am getting result like below:
Please help what i am doing wrong.
What you are trying to achieve is a ranking of a "group" so group the results by the points and then order the groups. For each item in the group give the same rank.
finalResult.GroupBy(item => item.Points) // Group by points
.OrderDescendingBy(g => g.Key) // Order the groups
.Select((g, index) => new { Data = g, GroupRank = index + 1}) // Rank each group
.SelectMany(g => g.Data.Select(item => new RankingEntity
{
/* properties of each item */
Rank = g.GroupIndex
}); // Flatten groups and set for each item the group's ranking
The problem in your method is that you give the ranking for individual items and not the group. Then when you retrieve the rank for the group (from i in finalResult let rank = finalResult.First(x => x.points == i.points)...) you actually set for each item in the group the ranking of one of the elements in it. Therefore, if you first got the last item of the group - that will be the Rank value of each item in it.
Also notice that in the first line of your code you use ToList. Therefore there is not need to use AsEnumerable in the line under it - it is already a materialized in memory collection.
I have a simple list of int with three elements, all of them are set to 1000.
If I group this list by values, I still get three elements instead of just one.
Why?
var l = new List<int> {1000, 1000, 1000};
var gr = from i in l
group i by new
{
j = i
}
into g1
from g in g1
select new
{
Id = g1.Key.j
};
var count = gr.Count(); // <- count is 3!
Loose the second from
var l = new List<int> {1000, 1000, 1000};
var gr = from i in l
group i by new
{
j = i
}
into g1
select new
{
Id = g1.Key.j
};
var count = gr.Count(); // <- count is 1!
That's because you are again projecting the grouped items. It is returning IEnumerable<IGrouping<int,int>> and you are enumerating IEnumerable<int> with from g in g1 which means you will get the items which are in group 1000 and thus the count 3.
Following query will give you correct result:-
var gr = from i in l
group i by i
into g1
select new
{
Id = g1.Key
};
gr.Count() will be 1 here since we are projecting the Key and not the items inside that group.
With Method Syntax:
You currect query is : l.GroupBy(x => x).SelectMany(x => x) so it will project all the items in the group thus Count 3.
If you want to count the Key then: l.GroupBy(x => x).Select(x => x.Key) this will return 1 since it will create a single group of 1000.
I think you're trying to achieve this:
var l = new List<pairs>
{
new pairs {Index = 0, Value = 1000},
new pairs {Index = 1, Value = 1000},
new pairs {Index = 2, Value = 1000},
};
var gr = l.GroupBy(a => a.Value);
var count = gr.Count(); // <- count is 1
Where Pairs is a simple POCO:
internal class pairs
{
public int Value { get; set; }
public int Index { get; set; }
}
The group by clause gives you the key along with all of the items that are in the group. You are selecting the items and not the key.
For example, try this:
var gr = from i in l
group i by i into g1
select g1;
var count = gr.Count();
var itemCount = gr.First().Count();
I need to sum elements of same type starting from 2 LINQ queries.
Below is my code:
var query1 = from d in _contextProvider.Context.Documents
where d.TransportId == transportId
group d by d.Type
into dg
select new { DocumentType = dg.Key.ToString(), DocumentCount = dg.Count() };
var query2 = from n in _contextProvider.Context.NotificationDocuments
where n.TransportId == transportId
group n by n.TransportId
into nd
select new { DocumentType = "Notification", DocumentCount = nd.Count() };
var query_collapsed = query1.Union(query2)
.GroupBy(p => new { DocumentType = p.DocumentType })
.Select(g => new DocumentCounters() { DocumentType = g.Key.DocumentType, DocumentCount = g.Sum(p => p.DocumentCount) });
Example: below let's analyse values for DocumentType equals to Notification.
Values of query1:
Values of query2:
The collapsed query :
That's correct: 1 + 2 = 3
The problem: I noticed that whenever the count for Notification in query1 is equals to the count for Notification in query2, then the sum is not performed.
Example:
2 + 2 = 2
or
3 + 3 = 3
Any ideas ?
LINQ Union will remove duplicate entries. If you want to merge the two sequences you can use Concat like so:
var query_collapsed = query1.Concat(query2)
.GroupBy(p => new { DocumentType = p.DocumentType })
.Select(g => new DocumentCounters() { DocumentType = g.Key.DocumentType, DocumentCount = g.Sum(p => p.DocumentCount) });
I have table 4 columns.
JobId StateId Salary Expense
1 1 35,000 31,000
1 1 33,000 25,000
1 2 28,000 26,000
2 2 7,000 16,000
2 2 6,000 20,000
2 1 9,000 22,000
2 1 15,000 29,000
By using LINQ in C#, i want to group by JobId and StateId combination.For each combination i want an array of Salary and array of Expense.
I can get one column as a array by for each combination, by using this
(from r in myTable.AsEnumerable()
group r by new {
jobId = r.Field<int>("JobId"),
stateId = r.Field<int>("StateId")
}).ToDictionary(
l => Tuple.Create(l.Key.jobId, l.Key.stateId),
l=> (from i in l select i.Field<double>("Salary")).AsEnumerable()
);
How can i have Salary and Expense in two array for each group??
My goal is to find average Salary and average Expense for each combination and do some other operation. Or at least tell me how can select multiple columns as separate array.
Note: I don't want collection of anonymous objects for each combination.
To select two different columns as collections in your query you can do this:
var result =
(from r in myTable.AsEnumerable()
group r by new
{
jobId = r.Field<int>("JobId"),
stateId = r.Field<int>("StateId")
} into g
select new
{
g.Key,
Salaries = g.Select(x => x.Field<double>("Salary")),
Expenses = g.Select(x => x.Field<double>("Expense"))
})
.ToDictionary(
l => Tuple.Create(l.Key.jobId, l.Key.stateId),
l => new { l.Salaries, l.Expenses }
);
Then you can compute the averages fairly easily:
var averageSalary = result[...].Salaries.Average();
var averageExpense = result[...].Expenses.Average();
But if all you really need is the averages, this will work:
var result =
(from r in myTable.AsEnumerable()
group r by new
{
jobId = r.Field<int>("JobId"),
stateId = r.Field<int>("StateId")
} into g
select new
{
g.Key,
AverageSalary = g.Average(x => x.Field<double>("Salary")),
AverageExpense = g.Average(x => x.Field<double>("Expense"))
})
.ToDictionary(
l => Tuple.Create(l.Key.jobId, l.Key.stateId),
l => new { l.AverageSalary, l.AverageExpense }
);
Do not use LINQ for this kind of statement. If you need to count the groupings and the compute some sort of average salary/expense you could try a list:
List<myType> myList = new List<myType>();
//add stuff to myList
List<myType> JobID1 = new List<myType();
List<myType> JobID2 = new List<myType();
foreach(var item in myList)
{
if(item.JobID == 1)
JobID1.add(item);
if(item.JobID == 2)
JobID2.add(item);
}
int avgSalOne;
foreach(var item in JobID1)
{
avgSalOne += item.Salary;
}
avgSalOne = avgSaleOne / JobID2.Count;
//Note that you get Job Id 2 average salary the same way, and also the Expense by changing item. Salary to item.Expense