Working with Arrays

[DaGarver]

I'm having some more trouble with working with arrays. My assignment is to take an input file of 10 numbers and display the original array, the array reversed (1st element is last element, etc.), the average of the parallel elements (nth element of both arrays), the average of the original array, and the elements greater than the average.

I know I need to load the file into an array. However, I can't seem to figure out how to reverse it, nor average the two even if I can get it reversed. Anyone have any suggestions?

[ForumAccount]

Since you clearly stated "assignment", can you post what code you have? And have tried?

[jakkjakk]

There's like list (of item) structures that can do all that stuff for you. But first things first, try! Since you are in school, lets school you a little bit. Attitude: You'll miss 100% of the time if you don't try!

[DaGarver]

First, I know how to get the file actually loaded as input.

If IO.File.Exists(filespec) Then
	sr = IO.File.OpenText(filespec)
Else
	msgbox(msg)
End If

I can also get the average of the array given.

total = 0
For cnt = 0 to UBound(numbers)
	total += numbers(cnt)
Next
avg1 = total/UBound(numbers)

And I can get the items greater than the average.

Do While num < UBound(numbers)
	var = numbers(num)
	If var > avg1 Then
		lstDisplay.Items.Add(var)
	End If
Loop

And I'm FAIRLY sure I can get the average of two parallel elements.

For cnt = 0 to UBound(numbers)
	avg2 = (numbers(cnt) + numbers(CInt(UBound(numbers)) - cnt))/2
	lstDisplay.Items.Add(avg2)
Next

However, as far as actually MAKING the arrays, I'm completely lost.

[jmcilhinney]

You know that there will be 10 numbers because the assignment says so, so you simply create an array with 10 elements and then use a For loop to read the data from the file into its elements. If you don't know how to create an array then I suggest that you read your notes because I very much doubt that they would have set this assignment without showing you that. Alternatively, do some online reading about arrays, e.g.

http://startvbdotnet.com/language/arrays.aspx

[DaGarver]

Okay, I got my data loaded into the arrays and have my output. However, the output seems rather...ridiculous. The average for the parallel elements and the elements greater than the average seem wrong.

Variable declarations:

Dim sr As IO.StreamReader
        Dim filespec As String = "numbers.txt"
        Dim msg As String = "Cannot open file: " & filespec
        Dim var As Double
        Dim cnt As Long
        Dim total, avg1 As Double
        Dim num As Integer = 0
        Dim array1() As String = IO.File.ReadAllLines(filespec)
        Dim array2(9) As String
        Dim arrayavg(9) As String

My code and the respective output:

Parallel Elements

For cnt = 0 To 9
            arrayavg(CInt(cnt)) = CStr(CDbl((array1(CInt(cnt)) + array2(CInt(cnt)))) / 2)
        Next
        lstDisplay.Items.Add("Average of Parallel Elements:")
        For cnt = 0 To 9
            lstDisplay.Items.Add(arrayavg(CInt(cnt)))
        Next
        lstDisplay.Items.Add("")

My output here is a lot of random numbers. For example, VB seems to think the average of 10 and 5 is 255. What? Any ideas?

Greater than Average

lstDisplay.Items.Add("Elements Greater than the Average:")
        Do While num < 9
            var = CDbl(array1(num))
            If var > avg1 Then
                lstDisplay.Items.Add(var)
            End If
            num += 1
        Loop

For this snippet of code, I get the output of 7, 8, 9, and 10. 6 SHOULD be included (the average of the array is 5.5). Any ideas why it isn't?

[jmcilhinney]

You should debug your code. Place a breakpoint at the top of a method using the F9 key. When execution stops at that point you can step line by line using the F10 key. You can also step into a method call using F11. You can now examine the values of all your variables at each step simply by mousing over them, or using the Locals and Autos windows.

At each step you check the values of your variables and decide what you think should happen when you step. You then step and check whether what you expected actually did happen. If it didn't then you've found an issue.