Vb.net how to display the frequency of digits from a text file

Question

I am still studying this stuff and been looking through google and Youtube but there doesn't seem to have this problem for VB.net I saw some on python or Java though. This is the output that I have to get but when i read the text file and try to find the frequency its doesn't go as hoped

This is my code.

Imports System.IO
Public Class Form1
    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles btnDisplay.Click

        Dim reader As TextReader = New StreamReader("number.txt")
        Dim num As Integer = 0

        For Each item In reader.ReadToEnd
            If item.CompareTo(reader.ReadLine) = True Then
                num += 1
            End If

        Next

        rtbshow.Text = "Digit" & " " & " " & " Frequency " & vbNewLine & reader.ReadToEnd() & " " & " " & num

    End Sub
End Class

Answer 1

A dictionary can work for this, but given just the nine digits an indexed array can do just as well and probably be faster.

Private Sub Button1_Click(sender As Object, e As EventArgs) Handles btnDisplay.Click
    Dim digitCounts = Enumerable.Repeat(0,10).ToArray()

    Dim digits = File.ReadAllText("number.txt").
                   Where(Function(c) Char.IsDigit(c)).
                   Select(Function(c) Asc(c) - Asc("0"c))
    For Each d As Integer In digits
        digitCounts(d) += 1
    Next
    Dim result As New StringBuilder($"Digit{vbTab}Frequency{vbCrLf}")
    For i As Integer = 0 To 9
        result.AppendLine($"{i,3}{vbTab}{digitCounts(i),7}")
    Next
    rtbshow.Text = result.ToString()
End Sub

You can (kind of) see it working here, except I couldn't get .Net fiddle to do the string interpolation:

https://dotnetfiddle.net/FMWnMg

We could also solve this with a GroupBy() operation:

Private Sub Button1_Click(sender As Object, e As EventArgs) Handles btnDisplay.Click
    Dim result As New StringBuilder($"Digit{vbTab}Frequency{vbCrLf}")
    Dim digits = File.ReadAllText("number.txt").
             Where(Function(c) Char.IsDigit(c)).
             OrderBy(Function(d) d).
             GroupBy(Function(d) d, 
                     Function(d, g) $"{d,3}{vbTab}{g.Count(),7}{vbCrLf}"
             )
    
    For Each d As String in digits
        result.Append(d)
    Next
    rtbshow.Text = result.ToString()
End Sub

See it work here:

https://dotnetfiddle.net/Xxl2z3

Note this last skips missing digits.