What is the best way to calculate word frequency in VB.NET?

Question

There are some good examples on how to calculate word frequencies in C#, but none of them are comprehensive and I really need one in VB.NET.

My current approach is limited to one word per frequency count. What is the best way to change this so that I can get a completely accurate word frequency listing?

wordFreq = New Hashtable()

Dim words As String() = Regex.Split(inputText, "(\W)")
    For i As Integer = 0 To words.Length - 1
        If words(i) <> "" Then
            Dim realWord As Boolean = True
            For j As Integer = 0 To words(i).Length - 1
                If Char.IsLetter(words(i).Chars(j)) = False Then
                    realWord = False
                End If
            Next j

            If realWord = True Then
                If wordFreq.Contains(words(i).ToLower()) Then
                    wordFreq(words(i).ToLower()) += 1
                Else
                    wordFreq.Add(words(i).ToLower, 1)
                End If
            End If
        End If
    Next

Me.wordCount = New SortedList

For Each de As DictionaryEntry In wordFreq
        If wordCount.ContainsKey(de.Value) = False Then
            wordCount.Add(de.Value, de.Key)
        End If
Next

I'd prefer an actual code snippet, but generic 'oh yeah...use this and run that' would work as well.

Answer 1

Public Class CountWords

    Public Function WordCount(ByVal str As String) As Dictionary(Of String, Integer)
        Dim ret As Dictionary(Of String, Integer) = New Dictionary(Of String, Integer)

        Dim word As String = ""
        Dim add As Boolean = True
        Dim ch As Char

        str = str.ToLower
        For index As Integer = 1 To str.Length - 1 Step index + 1
            ch = str(index)
            If Char.IsLetter(ch) Then
                add = True
                word += ch
            ElseIf add And word.Length Then
                If Not ret.ContainsKey(word) Then
                    ret(word) = 1
                Else
                    ret(word) += 1
                End If
                word = ""
            End If
        Next

        Return ret
    End Function

End Class

Then for a quick demo application, create a winforms app with one multiline textbox called InputBox, one listview called OutputList and one button called CountBtn. In the list view create two columns - "Word" and "Freq." Select the "details" list type. Add an event handler for CountBtn. Then use this code:

Imports System.Windows.Forms.ListViewItem

Public Class MainForm

    Private WordCounts As CountWords = New CountWords

    Private Sub CountBtn_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles CountBtn.Click
        OutputList.Items.Clear()
        Dim ret As Dictionary(Of String, Integer) = Me.WordCounts.WordCount(InputBox.Text)
        For Each item As String In ret.Keys
            Dim litem As ListViewItem = New ListViewItem
            litem.Text = item
            Dim csitem As ListViewSubItem = New ListViewSubItem(litem, ret.Item(item).ToString())

            litem.SubItems.Add(csitem)
            OutputList.Items.Add(litem)

            Word.Width = -1
            Freq.Width = -1
        Next
    End Sub
End Class

You did a terrible terrible thing to make me write this in VB and I will never forgive you.

:p

Good luck!

EDIT

Fixed blank string bug and case bug

Answer 2

This might be what your looking for:

    Dim Words = "Hello World ))))) This is a test Hello World"
    Dim CountTheWords = From str In Words.Split(" ") _
                        Where Char.IsLetter(str) _
                        Group By str Into Count()

I have just tested it and it does work

EDIT! I have added code to make sure that it counts only letters and not symbols.

FYI: I found an article on how to use LINQ and target 2.0, its a feels bit dirty but it might help someone http://weblogs.asp.net/fmarguerie/archive/2007/09/05/linq-support-on-net-2-0.aspx

Answer 3

Pretty close, but \w+ is a good regex to match with (matches word characters only).

Public Function CountWords(ByVal inputText as String) As Dictionary(Of String, Integer)
    Dim frequency As New Dictionary(Of String, Integer)

    For Each wordMatch as Match in Regex.Match(inputText, "\w+")
        If frequency.ContainsKey(wordMatch.Value.ToLower()) Then
            frequency(wordMatch.Value.ToLower()) += 1
        Else
            frequency.Add(wordMatch.Value.ToLower(), 1)
        End If
    Next
    Return frequency
End Function

Answer 4

This might be helpful:

Word frequency algorithm for natural language processing