VB 2010 Array Help

I need assistance with posting lines from a text file (test scores) into an array. From there, I'll have to average the test scores, find the standard deviation (without using the built in function) and assign grades based on the test scores' deviation. I have already written the code for the user to search and upload a text file. And I should be able to do the standard deviation of the array, if someone can help give me an example of how to send the text file to array and average the lines of the array without using the built in math functions.

Below is the code I currently have.

Thank you in advance.

Public Class Form1

Private Sub btnGo_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnGo.Click
Dim textFile As String
OpenFileDialog1.ShowDialog()
'
textFile = OpenFileDialog1.FileName
lstOut.DataSource = IO.File.ReadAllLines(textFile)
lstOut.SelectedItem = Nothing

End Sub
End Class

vb Code:

dim lines() as string =  IO.File.ReadAllLines(textFile)

Thanks, Paul, but then how do I go about calling the numbers to insert them into a function (averaging them, or calculating std deviation)?

what's your algorithm for calculating std deviation?

ok. try this then:

vb Code:

Public Class Form1
 
    Private Sub btnGo_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnGo.Click
        If OpenFileDialog1.ShowDialog() = Windows.Forms.DialogResult.OK Then
            'assuming each line of your text file contains a valid
            'decimal, + there are no empty lines in your file
            Dim numbers() As Decimal = Array.ConvertAll(IO.File.ReadAllLines(OpenFileDialog1.FileName), Function(s) CDec(s))
            Dim avg As Decimal = getAvg(numbers)
            Dim stdDeviation As Decimal = getStdDeviation(numbers)
        End If
    End Sub
 
    Private Function getAvg(ByVal d() As Decimal) As Decimal
        Return d.Average
    End Function
 
    Private Function getStdDeviation(ByVal d() As Decimal) As Decimal
        'run your code
        'Return std deviation
    End Function
 
End Class

s = sqrt(((x1-m)^2+(x2-m)^2+(x3-m)^2+...+(xn-m)^2)/n)

i'll let someone else help you with that. i got a headache before the = :D

It's just inserting each array value in the respective x1, x2, x3, etc. Which I've come to the realization that I don't know how to do that either.

ok. what is the value of m?
+ the value of n?

m = mean (the average)

try this:

vb Code:

Public Class Form1
 
    Private Sub btnGo_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnGo.Click
        If OpenFileDialog1.ShowDialog() = Windows.Forms.DialogResult.OK Then
            'assuming each line of your text file contains a valid
            'decimal, + there are no empty lines in your file
            Dim numbers() As Decimal = Array.ConvertAll(IO.File.ReadAllLines(OpenFileDialog1.FileName), Function(s) CDec(s))
            Dim avg As Decimal = getAvg(numbers)
            Dim stdDeviation As Decimal = getStdDeviation(numbers, avg)
        End If
    End Sub
 
    Private Function getAvg(ByVal d() As Decimal) As Decimal
        Return d.Average
    End Function
 
    Private Function getStdDeviation(ByVal d() As Decimal, avg as decimal) As Decimal
        Return Math.Sqrt(Array.ConvertAll(d, Function(n) (n - avg) ^ 2).Sum / d.length)
    End Function
 
End Class

to get the average without built in functions, you'd loop from 0 to d.getupperbound(0) + add each array element's value to a running total, then divide that by the array length

That works really well, Paul. At this point, I need to display the individual test scores, then run them through an if-else or case to display what grade they received based on the standard deviation.

If score >= avg + 1.4(stdDeviation)
Then grade = A
If score >= avg + .4(stdDeviation)
Then grade = B
etc.

Then I can output to list box fairly easily, but it's just pulling up the values from the array that I can't understand.

this is the output (copied from a msgbox) from my test app:

Quote:

---

---------------------------
Standard Deviation
---------------------------
Numbers:



2

4

4

4

5

5

7

9



Average: 5, Standard Deviation: 2
---------------------------
OK
---------------------------

---

the array d() = {2,4,4,4,5,5,7,9}

d(0) = 2
d(1) = 4
d(2) = 4
...
d(7) = 9

So I just use "d()" to call the values of the array?

You aren't really calling the values. D is the array. () is the VB operator for indexing into the array. Therefore, a line like:

d(5)

gets the 6th element of array d. Other languages use other array indexers, but it all works about the same.