CODEWITHSUNDEEP
arraysvbaexcel
S. Puri
S. Puri

Reputation: 11

Excel VBA function: How to pass range, convert to array, reverse, and return array

I am trying to do some array math in Excel which requires me to reverse a number of 1-dimensional ranges a good amount of times, so I want to write a function for it, rather than create reverses in the spreadsheet.

I have written a reverse() function in VBA but it returns #VALUE! errors in the spreadsheet. This happens no matter array size, nor whether inputting a same size array function or enclosing with a summary function like SUM(). I verified that the reversing logic works as a Sub. This leads me to believe the issue is with passing/returning the range/array but I don't understand what is wrong.

Function reverse(x As Range) As Variant()
' Array formula that reverses a one-dimensional array (1 row, x columns)
    Dim oldArray() As Variant, newArray() As Variant
    Dim rows As Long: i = x.rows.Count
    Dim cols  As Long: i = x.Columns.Count
    ReDim oldArray(1 To rows, 1 To cols), newArray(1 To rows, 1 To cols)

    oldArray = x.Value
    newArray = oldArray

    For i = 1 To cols / 2 Step 1
        newArray(1, i) = oldArray(1, cols - i + 1)
        newArray(1, cols - i + 1) = oldArray(1, i)
    Next

    reverse = newArray
End Function

Keep in mind, I may extend it to reverse 2 dimensional arrays, but that's the trivial part. My question is just trying to ensure the function works on a (1, N) range.

Thanks!

Upvotes: 1

Views: 2790

Answers (3)

Vincent G
Vincent G

Reputation: 3188

The following code is more versatile, it use optional arguments to determine if rows, columns or both (or none) should be reversed. By default it will reverse columns.

Function ReverseRange(Source As Range, Optional ReverseRows As Boolean = False, Optional ReverseColumns As Boolean = True) As Variant()
    Dim SourceArray() As Variant
    Dim DestArray() As Variant
    SourceArray = Source.value

    Dim nRows As Long, nColumns As Long
    nRows = UBound(SourceArray, 1)
    nColumns = UBound(SourceArray, 2)
    ReDim DestArray(1 To nRows, 1 To nColumns)

    Dim r As Long, r2 As Long, c As Long, c2 As Long
    For r = 1 To nRows
        r2 = IIf(ReverseRows, nRows - r + 1, r)
        For c = 1 To nColumns
            c2 = IIf(ReverseColumns, nColumns - c + 1, c)
            DestArray(r2, c2) = SourceArray(r, c)
        Next c
    Next r
    ReverseRange = DestArray
End Function

Note that there is no verification on the range validity.

Upvotes: 1

user6432984
user6432984

Reputation:

This will reverse the columns in the range no matter the row count.

Function reverse(Source As Range) As Variant()
    Dim Data, RevData
    Dim x As Long, y As Long, y1 As Long

    Data = Source.Value

    ReDim RevData(1 to UBound(Data, 1),1 to UBound(Data, 2))

    For x = 1 To UBound(Data, 1)
        y1 = UBound(Data, 2)
        For y = 1 To UBound(Data, 2)
            RevData(x, y1) = Data(x, y)
            y1 = y1 - 1
        Next
    Next
    reverse = RevData
End Function

Upvotes: 0

Aditya Pansare
Aditya Pansare

Reputation: 1132

Find below code....

Function reverse(x As Range) As Variant()
' Array formula that reverses a one-dimensional array (1 row, x columns)
    Dim oldArray() As Variant, newArray() As Variant
    Dim rows As Long
    rows = x.rows.Count
    Dim cols  As Long
    cols = x.Columns.Count
    ReDim oldArray(1 To rows, 1 To cols), newArray(1 To rows, 1 To cols)

    oldArray = x.Value
    newArray = oldArray

    For i = 1 To cols / 2 Step 1
        newArray(1, i) = oldArray(1, cols - i + 1)
        newArray(1, cols - i + 1) = oldArray(1, i)
    Next
reverse = newArray
End Function

Upvotes: 2

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