Redim Preserve Change LBOUND

[mailmaverick]

Hello


I have a single dimensional array in which I want to change lower bound, keeping the upper bound as same.


One way is to loop through the array and copy the desired values to a new variable. But, is there any shortcut or direct function ?

[mancubus]

assuming existing array holds (1, 2, 3, 4, 5, 6, 7, 8, 9, 10) and you want (6, 7, 8, 9, 10) in resultant array, try:

Sub vbax_55984_change_arrLB()

    Dim arrA
    Dim i As Long, NewLB As Long
    
    arrA = Array(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)
    NewLB = 5
    
    
    For i = NewLB To UBound(arrA)
        arrA(i - NewLB) = arrA(i)
    Next i
    
    ReDim Preserve arrA(UBound(arrA) - NewLB)

    'test    
    For i = LBound(arrA) To UBound(arrA)
        MsgBox "index is " & i & " - Element is " & arrA(i)
    Next

End Sub

yeah, loop

[snb]

Why would you want this ?

Lbound is 0 or 1.

[mancubus]

but if you want (1, 2, 3, 4, 5) in the final array, below procedure will do it:

Sub vbax_55984_change_arrLB() 
     
    Dim arrA 
    Dim i As Long, NewLB As Long 
     
    arrA = Array(1, 2, 3, 4, 5, 6, 7, 8, 9, 10) 
    NewLB = 5 
     
    ReDim Preserve arrA(NewLB To UBound(arrA)) 
     
End Sub

[Paul_Hossler]

Why would you want this ?

Lbound is 0 or 1.

LBound can be (almost) anything

I oft times use something like

Dim A (14 to 26) as String

For i = LBound(A) to UBound(A)
    A(i) = Cells(1,i).Value
Next i

[snb]

I don't see any advantage.

[Aflatoon]

But, is there any shortcut or direct function ?

Assuming you want to remove the entries from the start of the array, no. If you redim preserve and change the lower bound, you'll still lose the entries from the end. Also, you can only do it if your variable is actually declared as a Variant, not an array.

[Paul_Hossler]

I don't see any advantage.

Maybe so, but I find that the code is more readable than having a lot of things like "+14" etc

Dim A (12) As String 
 
For i = LBound(A) To UBound(A) 
    A(i) = Cells(1, i+14).Value 
Next i

I figure that since I've dealing with columns 14 to 26, why not just use 14-26 in the array

[Kenneth Hobs]

Try using row.

Sub vbax_55984_change_arrLB_2()    Dim arrA, i As Long, NewLB As Long
     
    arrA = Array(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)
    MsgBox Join(arrA, vbLf)
    
    NewLB = 5
    For i = NewLB To UBound(arrA)
        arrA(i - NewLB) = arrA(i)
    Next i
    ReDim Preserve arrA(UBound(arrA) - NewLB)
    MsgBox Join(arrA, vbLf)
End Sub


'snb arrays, http://www.snb-vba.eu/VBA_Arrays_en.html
'http://www.snb-vba.eu/VBA_Arrays_en.html#L_6.1
Sub vbax_55984_change_arrLB_3()
    Dim arrA, i As Long, NewLB As Long, arrB() As Variant
     
    arrA = Array(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)
    MsgBox Join(arrA, vbLf)
    
    NewLB = 5
    'arrB() = Application.Index(arrA, [row(5:10)])
    arrB() = Application.Index(arrA, Evaluate("=row(" & NewLB & ":10)"))
    Show2DArray arrB()
    MsgBox Join(Application.Transpose(arrB), vbLf)
End Sub


'similar to, http://www.cpearson.com/excel/vbaarrays.htmhttp://www.cpearson.com/excel/vbaarrays.htm
Public Sub Show2DArray(ByRef myArry() As Variant)  '<-- Note ByRef modifier.
  Dim x As Long
  Dim y As Long
  Dim s As String


  s = ""
  For y = LBound(myArry, 2) To UBound(myArry, 2)
    For x = LBound(myArry, 1) To UBound(myArry, 1)
      s = s & myArry(x, y) & ", "
    Next x
    If Mid(s, Len(s) - 1, 1) = "," Then s = Left(s, Len(s) - 2)
    s = s & vbNewLine
  Next y
  MsgBox s
End Sub

[mailmaverick]

HI All Thanks for your answers,

The reason for me to change the LBOUND of a single dimensional array is that I want to delete first few entries from the array. Is there any other solution to do this ?

[snb]

Why did they get there in the first place ?
You can ignore any value in any array without modifying the array.
You can 'remove/retain' any value in any 1-dimensional array using 'filter'.

[Paul_Hossler]

The reason for me to change the LBOUND of a single dimensional array is that I want to delete first few entries from the array. Is there any other solution to do this ?

1. Are the elements fixed length, intrinsic variables (Long, Double, etc.) not String?

2. Do you start with ary1(1 to 100) [= 100 elements]and then you only want ary2 (51 to 100) [= 50 elements] such that ary2(51) = ary1(51) ?

However, it's really not necessary to delete elements like that

[jonh]

Sub test()
    Dim c As New Collection
    
    'add 20 items
    For i = 1 To 20
        c.Add i
    Next
    
    'remove first 10
    For i = 1 To 10
        c.Remove 1
    Next
    
    'print remaining values
    For Each itm In c
        Debug.Print itm
    Next
End Sub

[snb]

A collection <> an Array

[jonh]

so?

[Kenneth Hobs]

There are 3 viable solutions and with a bit more work, another using jonh's collection method. I guess we could go at this for a long time to find many solutions. The row and filter methods are usually sufficient for my needs. snb's web site is best if you want to learn more about vba arrays.

This method is similar to rewriting the array method and the collection method. The main purpose is to show you the power that arraylist can provide.

'https://msdn.microsoft.com/en-us/library/system.array_methods(v=vs.110).aspx 'Array Methods
Sub Test_aRedim()
  Dim a() As Variant, i As Integer
  a() = Array("a", "b", "c", "d", "e", "f", "g", "h", "i", "j")
  MsgBox Join(a, vbLf)
  
  'a() = aRedim(a(), 4, 3)  'e,f,g
  a() = aRedim(a(), 4)      'e,f,g,h,i,j
  MsgBox Join(a(), vbLf)
End Sub


Function aRedim(a() As Variant, iFrom As Long, Optional iTo As Long = 0)
  Dim o As Object, i As Long
  
  If iTo = 0 Then
    iTo = UBound(a) - iFrom
  End If
  If LBound(a) = 0 Then iTo = iTo + 1
  
  Set o = CreateObject("System.Collections.ArrayList")
  With o
    For i = LBound(a) To UBound(a)
      .Add a(i)
    Next i
    aRedim = o.getrange(iFrom, iTo).Toarray()
  End With
End Function

[snb]

To 'remove' the first 5 items in this array:

Sub M_snb()
  sn = Array("a", "b", "c", "d", "e", "f", "g", "h", "i", "j")
  sn = Split(Trim(Split(Join(sn), sn(4))(1)))
End Sub