count the number of occurences of an element in an array

2008-12-07

Question

_{Sunday, December 7, 2008 1:31 AM}

i want to count the number of occurences of an element that are there in a 2d array. below is my code
Dim numbers(,) As Integer = {{1, 2}, _
        {4, 5}, _
        {7, 9}, _
        {3, 1}, _
        {2, 3}, _
        {5, 9}, _
        {8, 8}, _
        {9, 9}, _
        {7, 3}, _
        {2, 1}, _
        {5, 4}}

        Dim arrC(9) As Integer '= {0, 0, 0, 0, 0, 0, 0, 0, 0, 0}
        Dim rows As Integer
        Dim columns As Integer
        Dim i, counter, totalrows As Integer
        'totalrows = ((numbers.Length / 2) - 1)
        For i = 0 To 10
            For j = 0 To 1
                If arrC(numbers(i, j)) Then
                    MessageBox.Show(arrC(numbers(i, j)).ToString)
                    arrC(numbers(i, j)) += 1

                Else
                    arrC(numbers(i, j)) = 1
                End If
            Next
        Next
        For Each a_arrc In arrC
            MessageBox.Show(a_arrc.ToString)
        Next

can someone please help me try to fix the problem ?

All replies (10)

_{Sunday, December 7, 2008 3:13 AM ✅Answered | 1 vote}

Hi GJ111,

Welcome to the forums. :-)

Try a FOR EACH loop like this.

Try this code with one button on a FORM please.

Please note you said; "an element" not that you want to count every element occurrence.

Result = **There are 3 number 5's

**
Regards,

John

Option Strict On

Public Class Form1

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

Dim numbers(,) As Integer = _

{{1, 2}, {4, 5}, {7, 9}, {3, 1}, {2, 3}, {5, 9}, _

{8, 8}, {9, 9}, {7, 3}, {2, 1}, {5, 4}}

'To count the number of number 5's in the array called "numbers"

Dim count As Integer = 0

For Each num As Integer In numbers

If num = 5 Then count = count + 1

MessageBox.Show("There are " & count.ToString & " number 5's")

End Sub

End Class

For links to VB.Net tutorials see here.>> http://social.msdn.microsoft.com/Forums/en-US/vblanguage/thread/29f2179b-997b-4115-a96d-a0834853b835

_{Sunday, December 7, 2008 3:28 AM ✅Answered | 1 vote}

Hi again,

If you want to count each and every number then do this.

Add one button to a FORM to try this please.

Regards,

John

Option Strict On

Public Class Form1

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

Dim numbers(,) As Integer = _

{{1, 2}, {4, 5}, {7, 9}, {3, 1}, {2, 3}, {5, 9}, _

{8, 8}, {9, 9}, {7, 3}, {2, 1}, {5, 4}}

Dim counts(9) As Integer

For Each num As Integer In numbers

Select Case num

Case 0

counts(0) += 1

Case 1

counts(1) += 1

Case 2

counts(2) += 1

Case 3

counts(3) += 1

Case 4

counts(4) += 1

Case 5

counts(5) += 1

Case 6

counts(6) += 1

Case 7

counts(7) += 1

Case 8

counts(8) += 1

Case 9

counts(9) += 1

End Select

Dim sb As New System.Text.StringBuilder

For index As Integer = 0 To 9

sb.Append("There are " & counts(index).ToString & " number " & index.ToString & "'s found." & ControlChars.NewLine)

MessageBox.Show(sb.ToString)

End Sub

End Class

For links to VB.Net tutorials see here.>> http://social.msdn.microsoft.com/Forums/en-US/vblanguage/thread/29f2179b-997b-4115-a96d-a0834853b835

_{Monday, December 8, 2008 9:39 AM ✅Answered | 1 vote}

Hi,
John's answer is quite good for the question. And I just do a little modification in the following way:

Public Class Form1

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim numbers(,) As Integer = _
        {{1, 2}, {4, 5}, {7, 9}, {3, 1}, {2, 3}, {5, 9}, _
            {8, 8}, {9, 9}, {7, 3}, {2, 1}, {5, 4}}

        Dim counts(9) As Integer
        For Each num As Integer In numbers
            If num >= 0 And num < 10 Then
                counts(num) += 1
            End If
        Next

        Dim sb As New System.Text.StringBuilder
        For index As Integer = 0 To 9
            sb.Append(index.ToString & ": " & counts(index).ToString & ControlChars.NewLine)
        Next
        MessageBox.Show(sb.ToString)

End Sub
End Class

_{Monday, December 8, 2008 11:58 AM ✅Answered | 1 vote}

this will work with any integers in numbers. if the range of numbers is large another approach would be better.

Dim numbers(,) As Integer = {{1, 2}, _

{4, 5}, _

{7, 9}, _

{3, 1}, _

{2, 3}, _

{5, 9}, _

{8, 8}, _

{9, 9}, _

{7, 3}, _

{2, 1}, _

{13, 20}, _

{19, 21}, _

{5, 4}}

Dim arrC As New List(Of Integer)

Dim nRow As Integer, nCol As Integer

For nRow = 0 To numbers.GetUpperBound(0)

For nCol = 0 To numbers.Rank - 1

If numbers(nRow, nCol) >= arrC.Count Then

Do While numbers(nRow, nCol) >= arrC.Count

arrC.Add(0)

Loop

End If

arrC(numbers(nRow, nCol)) += 1

Dim sb As New System.Text.StringBuilder

For i As Integer = 0 To arrC.Count - 1

sb.Append(i.ToString.PadRight(8, " "c))

sb.Append(arrC(i).ToString)

sb.Append(Environment.NewLine)

MessageBox.Show(sb.ToString)

Stop

_{Tuesday, December 9, 2008 8:35 PM ✅Answered | 1 vote}

If you're using VB2008, then LINQ and Llamda functions come in very handy:

Public Class Program

Public Shared Sub Main()

Dim vehicles() As Vehicle = { _

New Vehicle("Car", "Red", "Ferrari"), _

New Vehicle("Truck", "Green", "Ford"), _

New Vehicle("Truck", "White", "Chevy"), _

New Vehicle("Car", "Blue", "Aston Martin"), _

New Vehicle("Car", "Red", "Porsche"), _

New Vehicle("Truck", "Brown", "Toyota"), _

New Vehicle("Car", "Orange", "Honda"), _

New Vehicle("Car", "Blue", "Toyota"), _

New Vehicle("Truck", "Orange", "Dodge") _

}

'using Llambda functions

Dim redFerraris = vehicles.Where(Function(v) v.Make = "Ferrari" AndAlso v.Color = "Red")

Dim blueCars = vehicles.Where(Function(v) v.Type = "Car" AndAlso v.Color = "Blue")

        'using LINQ
        Dim trucks = From v In vehicles _
                   Where v.Type = "Truck" _
                     Select v

        Dim linqRedFerraris = From v1 In vehicles _
                        Where v1.Make = "Ferrari" AndAlso v1.Color = "Red" _
                        Select v1

Console.ReadLine()

End Sub

End Class

Public Class Vehicle

Public Type As String

Public Color As String

Public Make As String

Public Sub New()

End Sub

Public Sub New(ByVal t As String, ByVal c As String, ByVal m As String)

Type = t

Color = c

Make = m

End Sub

End Class

I used a simple class for Vehicle with nothing but public string fields for the example, to keep it short.

This same sort of thing can be accomplished in VB2005 by using the Array.FindAll method in conjunction with a delegate.

Chris

_{Tuesday, December 9, 2008 1:14 PM | 1 vote}

Hi ALL,

I thought I would add an updated version. :-) ;-)

By the way thanks typot for your idea. :-)

This version does not show any value where the count is zero.

I thought what is the point in showing a zero count?

It will also only work for INTEGER values greater than or equal to zero so the array is declared as

UInteger which means an Unsigned Integer.

Again this code has a limited range depending on what the highest number in the array of numbers is.

Regards,

John

Option Strict On

Public Class Form1

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

Dim numbers(,) As UInteger = _

{{1, 2}, {4, 5}, {765, 9}, {3, 1}, {2, 3}, {5, 9}, _

{8, 8}, {9, 9}, {765, 3}, {2, 1}, {5, 1000}}

Dim numbersList As New List(Of UInteger)

For Each num As UInteger In numbers

numbersList.Add(num)

Try

Dim newArray() As UInteger = numbersList.ToArray

Array.Sort(newArray)

Dim counts(CInt(newArray(newArray.GetUpperBound(0)))) As Integer

For Each num As UInteger In newArray

If num >= 0 And num <= newArray(newArray.GetUpperBound(0)) Then

counts(CInt(num)) += 1

End If

Dim sb As New System.Text.StringBuilder

For index As Integer = CInt(newArray(newArray.GetLowerBound(0))) To CInt(newArray(newArray.GetUpperBound(0)))

If counts(index) <> 0 Then

sb.Append(index.ToString & ": " & counts(index).ToString & ControlChars.NewLine)

End If

MessageBox.Show(sb.ToString)

Catch ex As Exception

MessageBox.Show(ex.ToString)

End Try

End Sub

End Class

For links to VB.Net tutorials see here.>> http://social.msdn.microsoft.com/Forums/en-US/vblanguage/thread/29f2179b-997b-4115-a96d-a0834853b835

_{Tuesday, December 9, 2008 1:35 PM | 1 vote}

Hi ALL,

Here is an INTEGER version of the above code but a rethink would be need as the -999 is not detected.

This is because negative array indexes are not allowed in Vb.Net.

Regards,

John

Option Strict On

Public Class Form1

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

Dim numbers(,) As Integer = _

{{1, 2}, {4, 5}, {765, -999}, {3, 1}, {2, 3}, {5, 9}, _

{8, 8}, {9, 9}, {765, 3}, {2, 1}, {5, 1000}}

Dim numbersList As New List(Of Integer)

For Each num As Integer In numbers

numbersList.Add(num)

Try

Dim newArray() As Integer = numbersList.ToArray

Array.Sort(newArray)

Dim counts(CInt(newArray(newArray.GetUpperBound(0)))) As Integer

For Each num As Integer In newArray

If num >= 0 And num <= newArray(newArray.GetUpperBound(0)) Then

counts(CInt(num)) += 1

End If

Dim sb As New System.Text.StringBuilder

For index As Integer = 0 To CInt(newArray(newArray.GetUpperBound(0)))

If counts(index) <> 0 Then

sb.Append(index.ToString & ": " & counts(index).ToString & ControlChars.NewLine)

End If

MessageBox.Show(sb.ToString)

Catch ex As Exception

MessageBox.Show(ex.ToString)

End Try

End Sub

End Class

For links to VB.Net tutorials see here.>> http://social.msdn.microsoft.com/Forums/en-US/vblanguage/thread/29f2179b-997b-4115-a96d-a0834853b835

_{Tuesday, December 9, 2008 2:24 PM}

Hi ALL,

So what I mention above leads me to another interesting problem.

How would you count the occurrence of each of the various OBJECTs in an array as well count the occurrence of each of the numbers even if they are positive or negative?

1) Say we count the occurrence of each of the numbers that are zero and above, now we want to count the occurrence of each of the numbers below zero as well as count the occurrence of each of the other objects that are identical. How could we do that?

Say we have 2 Red Ferrari cars and lots of other cars, how could we count the objects of TYPE = CAR or say count the number of RED cars or say count the number of Ferrari cars.

Now you might be thinking this is erring on databases and SQL queries and you would be right.

2) For a second but similar problem, I am thinking of 1 general routine to count each number whether positive or negative as well as simply count the objects of a particular TYPE, such as count the STRINGs, and count each occurence of each number too.

I guess both problems would possibly be solved in
conjuction with a COMPARER and a DICTIONARY maybe?

Regards,

John

For links to VB.Net tutorials see here.>> http://social.msdn.microsoft.com/Forums/en-US/vblanguage/thread/29f2179b-997b-4115-a96d-a0834853b835

_{Tuesday, December 9, 2008 9:43 PM}

findall only works for one dimensional arrays.

_{Wednesday, December 10, 2008 3:24 AM}

Chris Dunaway said:

If you're using VB2008, then LINQ and Llamda functions come in very handy:

I used a simple class for Vehicle with nothing but public string fields for the example, to keep it short.

This same sort of thing can be accomplished in VB2005 by using the Array.FindAll method in conjunction with a delegate.

Chris

Hi Chris,

Thanks for your code, your post, your time etcetera.

LINQ and Llamda functions are some of the other things I need to look into and learn.

I have already done SQL at university recently on my current course so I can see the SQL style statements in your code.

Thanks again. :-)

Regards,

John

For links to VB.Net tutorials see here.>> http://social.msdn.microsoft.com/Forums/en-US/vblanguage/thread/29f2179b-997b-4115-a96d-a0834853b835

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count the number of occurences of an element in an array

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