How make concatenate function faster

Question

Hi everyone hope you are doing well. I have a code that depends on a concatenate process to be used later. The piece of code where I make the concatenate is the following:

i=2 
Do while ws.cells(i,2) <> 0
 ws.cells(i,1) = "=concatenate(C" & i & ", D" & i & ")" 
 i = i + 1 
Loop

The problem is if I have a big sample, it takes too much time to complete. Do you guys know any way to make it better and faster? Thanks in advance

Answer 1

Difference between Formulas and Arrays:

Formula - Total Rows: 1,048,576, Time: 2.414 sec
Arrays  - Total Rows: 1,048,576, Time: 3.758 sec

---

Option Explicit

Public Sub JoinCDinA1()
    Dim ws As Worksheet, lr As Long, tr As String, t As Double

    t = Timer
    Set ws = Sheet1
    lr = ws.UsedRange.Rows.Count

    With ws.Range("A2:A" & ws.UsedRange.Rows.Count)
        .Formula = "= C2 & D2"
        .Value2 = .Value2
    End With

    tr = "Formula - Total Rows: " & Format(lr, "#,###,###")
    Debug.Print tr & ", Time: " & Format(Timer - t, "0.000") & " sec"
End Sub

Public Sub JoinCDinA2()
    Dim ws As Worksheet, ur1 As Variant, ur2 As Variant, r As Long, lr As Long
    Dim tr As String, t As Double

    t = Timer
    Set ws = Sheet1
    lr = ws.UsedRange.Rows.Count
    ur1 = ws.Range(ws.Cells(2, 1), ws.Cells(lr, 1))
    ur2 = ws.Range(ws.Cells(2, 3), ws.Cells(lr, 4))
    For r = 1 To lr - 1
        ur1(r, 1) = ur2(r, 1) & ur2(r, 2)
    Next
    ws.Range(ws.Cells(2, 1), ws.Cells(lr, 1)) = ur1

    tr = "Arrays  - Total Rows: " & Format(lr, "#,###,###")
    Debug.Print tr & ", Time: " & Format(Timer - t, "0.000") & " sec"
End Sub