# help with array, ifthen, loop

[code]
2d_array = getrows()

'2d_array(1,20)
'column1, column2
'1,1
'1,2
'1,3
'1,1
'1,2
'1,3
'1,1
'1,2
'1,3
'2,1
'2,2
'2,3
'2,1
'2,2
'2,3
'2,1
'2,2
'2,3
'2,1
'2,2
'2,3

a = 0
b = 0
Redim zz(0,0)
Do While a < Ubound(2d_array,2)
If 2d_array(1,a) = 1 Then
If PreviousRow <> "" Then PreviousRow = 2d_array(0,a)

If PreviousRow = 2d_array(0,a) Then
Redim preserve zz(0,b)
zz(0,b) = zz(0,b) + 1
End If

If PreviousRow <> 2d_array(0,a) Then
b = b + 1
Redim preserve zz(0,b)
zz(0,b) = 1
PreviousRow = 2d_array(0,a)
End If
End If
a = a + 1
Loop

[/code]

I'm trying to make this work but it doesn't seem to want to follow my (flawed) logic. As you can see, I am using the 2nd column as the main counter. Whenever 2d_array(1,a) = 1, the IfThen statements will be exectued.

When it first loops, the code:

If PreviousRow <> "" Then PreviousRow = 2d_array(0,a)

will initialize PreviousRow to the first 2d_array row. So PreviousRow would equal to 1 in this case upon the first loop.

The 2nd If statement:

If PreviousRow = 2d_array(0,a) Then
Redim preserve zz(0,b)
zz(0,b) = zz(0,b) + 1
End If

Since PreviousRow = 1 and 2d_array(0,0) = 1 also then zz(0,b) = zz(0,b) + 1. So actually zz(0,0) = 1 at this point.

The 3rd If statment:

If PreviousRow <> 2d_array(0,a) Then
b = b + 1
Redim preserve zz(0,b)
zz(0,b) = 1
PreviousRow = 2d_array(0,a)
End If

Since PreviousRow = 1 and 2d_array(0,0) = 1 are the same, this code is not executed until 2d_array(0,9). If it finds a difference, then it starts a new row.

Finally, the final output of the zz array should be:

zz(0,0) = 3
zz(0,1) = 4

Right now my incorrect output is:

zz(0,0) = "" (nothing)
zz(0,1) = 7

Hopefully I made myself clear...
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High School Computer Science, Computer Applications, and Mathematics TeachersCommented:
I think this does what you want...

Option Explicit

Private my2dArray(1, 20) As Integer
Private zz() As Integer

Dim i As Integer
Dim cnt As Integer
For i = 0 To 20
If i <= 8 Then
my2dArray(0, i) = 1
Else
my2dArray(0, i) = 2
End If

cnt = cnt + 1
If cnt = 4 Then
cnt = 1
End If
my2dArray(1, i) = cnt
Next i

Debug.Print "my2dArray"
For i = 0 To UBound(my2dArray, 2)
Debug.Print i & ": " & my2dArray(0, i) & "," & my2dArray(1, i)
Next i
Debug.Print
End Sub

Private Sub Command1_Click()
Dim i As Integer
Dim PreviousRow As Integer
Dim cnt As Integer
Dim rows As Integer

ReDim zz(0, 0)
PreviousRow = -1
rows = -1
For i = 0 To UBound(my2dArray, 2)
If my2dArray(1, i) = 1 Then
If PreviousRow = -1 Then
PreviousRow = my2dArray(0, i)
cnt = 1
ElseIf my2dArray(0, i) = PreviousRow Then
cnt = cnt + 1
Else
PreviousRow = my2dArray(0, i)
rows = rows + 1
ReDim Preserve zz(0, rows)
zz(0, rows) = cnt
cnt = 1
End If
End If
Next i
rows = rows + 1
ReDim Preserve zz(0, rows)
zz(0, rows) = cnt

Debug.Print "zz()"
For i = 0 To UBound(zz, 2)
Debug.Print zz(0, i)
Next i
End Sub

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