average with items in an array

[jac130]

I have an array, populated with student grades. there is a list of student names, but their grades are stored in a class level array. there is a calculate average button,that is supposed to calculate the grades in the array. But my button only returns the last grade that was entered, not the average, here is my code:

public Class btnAdd
    Dim grades() As Double


    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim name As String = InputBox("please enter a student's name.")
        'validate name
        Do While Not isvalidname(name)
            name = InputBox("please enter a student's name.")
        Loop
        'display info
        lstStudents.Items.Add(name)

        'validate grade
        Dim grade As String = InputBox("please enter a positive number for grades.")
        Do While Not IsPositiveNumber(grade)
            grade = InputBox("please enter a positive number for grades.")
        Loop
        'populate array
        Dim i As Integer
        Dim size As Integer = lstStudents.Items.Count
        ReDim grades(size - 1)
        For i = 0 To grades.GetUpperBound(0)
            grades(i) = CDbl(grade)
        Next
    End Sub
    Function getaverage(ByVal grades() As Double) As Double
        'validate input
        Dim sum As Double = 0
        Dim i As Double
        'loop to find the average 
        For i = 0 To grades.GetUpperBound(0)
            sum = sum + grades(i) / lstStudents.Items.Count
        Next
        'return average 
        Return MsgBox("The average is " & FormatNumber(sum))

    End Function

    Private Sub btnAverage_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnAverage.Click
        'call getaverage function
        getaverage(grades)
    End Sub

[jac130]

I'm not sure if i'm atucally populating the array, or it's jsut keeping the last value put into it. I tried the redim preserve keywords, but if i click the average button, it only gives me the average using the last grade entered,, not the sum of all of them. : here is my code for it:

Public Class btnAdd
    Dim grades() As Double

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

        Dim name As String = InputBox("please enter a student's name.")
        'validate name
        Do While Not isvalidname(name)
            name = InputBox("please enter a student's name.")
        Loop
        'display info
        lstStudents.Items.Add(name)

        'validate grade
        Dim grade As String = InputBox("please enter a positive number for grades.")
        Do While Not IsPositiveNumber(grade)
            grade = InputBox("please enter a positive number for grades.")
        Loop
        'populate array
        Dim i As Integer
        Dim size As Integer = lstStudents.Items.Count
        ReDim Preserve grades(i)
        For i = 0 To grades.GetUpperBound(0)
            grades(i) = CDbl(grade)
        Next
    End Sub

    Function getaverage(ByVal grades() As Double) As Double
        'validate input
        Dim sum As Integer
        Dim i As Integer
        'loop to find the average 
        
        For i = 0 To grades.GetUpperBound(0)
            ReDim Preserve grades(i)
            sum = sum + Val(grades(i)) / lstStudents.Items.Count
        Next
        'return average 
        Return MsgBox("The average is " & FormatNumber(sum))

    End Function

    Private Sub btnAverage_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnAverage.Click
        'call getaverage function
        getaverage(grades)
    End Sub

[lotus18]

Are you sure you were adding the names in the listbox?
OK. Here's the algo:

1. Get the name of the student
2. Get the grades of the student
3. Compute for the average grade
4. Proceed to the next student when you are done and follow steps 2-3 until the condition is met.
5. Compute for the total average
   

My 2nd option is create a temporary variable that will hold temporary values : )

Rey Sean