How to improve a VBA macro that is reading a file slowly

Question

On a recent project I need to read from a file that contains around 5K lines.

Each line has different fields and I need to collect some of them into specific cells in excel. Example of one line:

data1;data2;data3; ..... ;dataN\\r

N can be as large as 600.

Currently I'm opening the file and looping through each line, splitting by ";" and saving.

What I need is an example:

avarSplit = Split(sBuf, ";")

Range("C" & i).Value = CDbl(avarSplit(meter))

This tends to be extremely slow and I already have,

Application.Calculation = xlCalculationManual

Answer 1

I'd recommend asking VBA to open the file as a delimited text file (the equivalent of File->Open, select , then choosing 'delimited' and ';' in the open text file wizard). If you need to see how to do that in VBA, record a macro, then open it manually. Then you have your split values in a temporary workbook, and can copy them into your worksheet as before.

Answer 2

5k lines, even with 600 columns shouldn't take that long. It's likely that the hold up is writing the values to the cells. It would be better to fill a two-dim output array and write the values to the spreadsheet all in one go. Here's an example.

Sub ReadTextFile()

    Dim sFile As String
    Dim lFile As Long
    Dim vaLines As Variant, vaSplit As Variant
    Dim aOutput() As String
    Dim i As Long
    Dim sInput As String

    sFile = MyDocs & "Book4.csv"
    lFile = FreeFile

    'Read in data
    Open sFile For Input As lFile
    sInput = Input$(LOF(lFile), lFile)
    'Split on new line
    vaLines = Split(sInput, vbNewLine)

    'Set up output array - split is zero based
    'but you want 1-based to write to cells
    ReDim aOutput(1 To UBound(vaLines, 1) + 1, 1 To 1)

    'loop through lines
    For i = LBound(vaLines) To UBound(vaLines)
        If Len(vaLines(i)) > 0 Then
            'split on delimiter
            vaSplit = Split(vaLines(i), ";")
            'store want you want in the output array
            aOutput(i + 1, 1) = vaSplit(15)
        End If
    Next i

    'write the output array to a range
    Sheet1.Range("A2").Resize(UBound(aOutput, 1), UBound(aOutput, 2)).Value = aOutput

End Sub