Method DenseRank

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DenseRank<TSource>(IEnumerable<TSource>)

Ranks each item in the sequence in ascending order using a default comparer, with no gaps in the ranking values. The rank starts at one and keeps incrementing by one for each different item.

Declaration
public static IEnumerable<(TSource item, int rank)> DenseRank<TSource>(this IEnumerable<TSource> source)
Parameters
Type Name Description
IEnumerable<TSource> source

The sequence whose items will be ranked
Returns
Type Description
IEnumerable<(TSource item, int rank)>

A sorted sequence of items and their rank.
Type Parameters
Name Description
TSource

Type of item in the sequence
Remarks

This method is implemented by using deferred execution. However, source will be consumed in it's entirety immediately when first element of the returned sequence is consumed.

Examples

The following code example demonstrates how to rank the items in a sequence using DenseRank.

var sequence = new Item[]
{
    new(key: 5, text: "1"),
    new(key: 5, text: "2"),
    new(key: 4, text: "3"),
    new(key: 4, text: "4"),
    new(key: 3, text: "5"),
    new(key: 3, text: "6"),
    new(key: 2, text: "7"),
    new(key: 2, text: "8"),
    new(key: 1, text: "9"),
    new(key: 1, text: "10"),
};

// Rank the items in the sequence
var result = sequence.DenseRank();

Console.WriteLine(
    "[" +
    string.Join(", ", result) +
    "]");

// This code produces the following output:
// [((1, 9), 1), ((1, 10), 1), ((2, 7), 2), ((2, 8), 2), ((3, 5), 3), ((3, 6), 3), ((4, 3), 4), ((4, 4), 4), ((5, 1), 5), ((5, 2), 5)]

class Item : IComparable<Item>
{
    public Item(int key, string text)
    {
        Key = key;
        Text = text;
    }

    public int Key { get; }
    public string Text { get; }

    public int CompareTo(Item other) =>
        this.Key.CompareTo(other.Key);

    public override string ToString() =>
        $"({this.Key}, {this.Text})"; 
}
Exceptions
Type Condition
ArgumentNullException

source is null.
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DenseRank<TSource>(IEnumerable<TSource>, OrderByDirection)

Ranks each item in the sequence in the order defined by sortDirection using a default comparer, with no gaps in the ranking values. The rank starts at one and keeps incrementing by one for each different item.

Declaration
public static IEnumerable<(TSource item, int rank)> DenseRank<TSource>(this IEnumerable<TSource> source, OrderByDirection sortDirection)
Parameters
Type Name Description
IEnumerable<TSource> source

The sequence whose items will be ranked
OrderByDirection sortDirection

Defines the ordering direction for the sequence
Returns
Type Description
IEnumerable<(TSource item, int rank)>

A sorted sequence of items and their rank.
Type Parameters
Name Description
TSource

Type of item in the sequence
Remarks

This method is implemented by using deferred execution. However, source will be consumed in it's entirety immediately when first element of the returned sequence is consumed.

Examples

The following code example demonstrates how to rank the items in a sequence using DenseRank.

var sequence = new Item[]
{
    new(key: 5, text: "1"),
    new(key: 5, text: "2"),
    new(key: 4, text: "3"),
    new(key: 4, text: "4"),
    new(key: 3, text: "5"),
    new(key: 3, text: "6"),
    new(key: 2, text: "7"),
    new(key: 2, text: "8"),
    new(key: 1, text: "9"),
    new(key: 1, text: "10"),
};

// Rank the items in the sequence
var result = sequence.DenseRank(OrderByDirection.Ascending);

Console.WriteLine(
    "[" +
    string.Join(", ", result) +
    "]");

// This code produces the following output:
// [((1, 9), 1), ((1, 10), 1), ((2, 7), 2), ((2, 8), 2), ((3, 5), 3), ((3, 6), 3), ((4, 3), 4), ((4, 4), 4), ((5, 1), 5), ((5, 2), 5)]

class Item : IComparable<Item>
{
    public Item(int key, string text)
    {
        Key = key;
        Text = text;
    }

    public int Key { get; }
    public string Text { get; }

    public int CompareTo(Item other) =>
        this.Key.CompareTo(other.Key);

    public override string ToString() =>
        $"({this.Key}, {this.Text})"; 
}
Exceptions
Type Condition
ArgumentNullException

source is null.
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DenseRank<TSource>(IEnumerable<TSource>, IComparer<TSource>)

Ranks each item in the sequence in ascending order using a caller-supplied comparer, with no gaps in the ranking values. The rank starts at one and keeps incrementing by one for each different item.

Declaration
public static IEnumerable<(TSource item, int rank)> DenseRank<TSource>(this IEnumerable<TSource> source, IComparer<TSource> comparer)
Parameters
Type Name Description
IEnumerable<TSource> source

The sequence of items to rank
IComparer<TSource> comparer

A object that defines comparison semantics for the elements in the sequence
Returns
Type Description
IEnumerable<(TSource item, int rank)>

A sorted sequence of items and their rank.
Type Parameters
Name Description
TSource

The type of the elements in the source sequence
Remarks

This method is implemented by using deferred execution. However, source will be consumed in it's entirety immediately when first element of the returned sequence is consumed.

Examples

The following code example demonstrates how to rank the items in a sequence using DenseRank.

var sequence = new[]
{
    (key: 5, text: "1"),
    (key: 5, text: "2"),
    (key: 4, text: "3"),
    (key: 4, text: "4"),
    (key: 3, text: "5"),
    (key: 3, text: "6"),
    (key: 2, text: "7"),
    (key: 2, text: "8"),
    (key: 1, text: "9"),
    (key: 1, text: "10"),
};

// Get the top N sets of items
var result = sequence
    .DenseRank(
        Comparer<(int key, string text)>.Create((x, y) => x.key.CompareTo(y.key)));

Console.WriteLine(
    "[" +
    string.Join(", ", result) +
    "]");

// This code produces the following output:
// [((1, 9), 1), ((1, 10), 1), ((2, 7), 2), ((2, 8), 2), ((3, 5), 3), ((3, 6), 3), ((4, 3), 4), ((4, 4), 4), ((5, 1), 5), ((5, 2), 5)]
Exceptions
Type Condition
ArgumentNullException

source is null.
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DenseRank<TSource>(IEnumerable<TSource>, IComparer<TSource>, OrderByDirection)

Ranks each item in the sequence in the order defined by sortDirection using a caller-supplied comparer, with no gaps in the ranking values. The rank starts at one and keeps incrementing by one for each different item.

Declaration
public static IEnumerable<(TSource item, int rank)> DenseRank<TSource>(this IEnumerable<TSource> source, IComparer<TSource> comparer, OrderByDirection sortDirection)
Parameters
Type Name Description
IEnumerable<TSource> source

The sequence of items to rank
IComparer<TSource> comparer

A object that defines comparison semantics for the elements in the sequence
OrderByDirection sortDirection

Defines the ordering direction for the sequence
Returns
Type Description
IEnumerable<(TSource item, int rank)>

A sorted sequence of items and their rank.
Type Parameters
Name Description
TSource

The type of the elements in the source sequence
Remarks

This method is implemented by using deferred execution. However, source will be consumed in it's entirety immediately when first element of the returned sequence is consumed.

Examples

The following code example demonstrates how to rank the items in a sequence using DenseRank.

var sequence = new[]
{
    (key: 5, text: "1"),
    (key: 5, text: "2"),
    (key: 4, text: "3"),
    (key: 4, text: "4"),
    (key: 3, text: "5"),
    (key: 3, text: "6"),
    (key: 2, text: "7"),
    (key: 2, text: "8"),
    (key: 1, text: "9"),
    (key: 1, text: "10"),
};

// Get the top N sets of items
var result = sequence
    .DenseRank(
        Comparer<(int key, string text)>.Create((x, y) => x.key.CompareTo(y.key)),
        OrderByDirection.Ascending);

Console.WriteLine(
    "[" +
    string.Join(", ", result) +
    "]");

// This code produces the following output:
// [((1, 9), 1), ((1, 10), 1), ((2, 7), 2), ((2, 8), 2), ((3, 5), 3), ((3, 6), 3), ((4, 3), 4), ((4, 4), 4), ((5, 1), 5), ((5, 2), 5)]
Exceptions
Type Condition
ArgumentNullException

source is null.