API reference · Arrays

DimReduce

Convert a single-row or single-column 2D array into a 1D array.

FunctionArrays→VariantSource L256

Signature#

Function DimReduce(ByVal vArr As Variant) As Variant

Parameters#

Parameter	VBA type	Default	Description
`vArr`	`Variant`ByVal	Required	Allocated 2D array with exactly one row or exactly one column.

Returns#

Variant containing a 1D array. A single row uses the source column bounds; a single column uses the source row bounds. Returns Empty for non-arrays, other ranks, or a matrix with multiple rows and multiple columns.

Example#

SEE THE TRANSFORMATIONRemove the single-column dimension

Before

amountColumn2D · 3 × 1

Rows 5..7 · Columns 1..1

row / col	1
5	120
6	80
7	50

After

amounts1D · (3,)

Indices 5..7 · one dimension

5	6	7
120	80	50

A 1D vector has one index per element. It is drawn horizontally here for readability; it is not a 1 × 3 matrix.

Shaded headers are array indices, not data. Quoted cells are text. Values shown are derived from the source, not an Excel execution.

Sub ExampleDimReduce()
    Dim a As New Arrays
    Dim amountColumn As Variant, amounts As Variant

    ReDim amountColumn(5 To 7, 1 To 1)
    amountColumn(5, 1) = 120
    amountColumn(6, 1) = 80
    amountColumn(7, 1) = 50
    amounts = a.DimReduce(amountColumn)
    Debug.Print LBound(amounts), UBound(amounts) ' Expected: 5, 7
    Debug.Print amounts(6)                    ' Expected: 80
End Sub

Behavior and edge cases#

The single-row branch is checked first. For a 1 × 1 array, the sole output subscript comes from the source column bound.
A general matrix is not flattened. It returns Empty when neither dimension has exactly one element.
The remaining dimension's lower and upper bounds are preserved, and values stay in source order.
Empty, Null and error-valued elements are copied. The input array is not modified.

Performance#

O(n) time and O(n) output storage, where n is the length of the surviving dimension.

View implementation

Function DimReduce(ByVal vArr As Variant) As Variant
    'Converts a single-row or single-column 2D array into a 1D array

    Dim vArr_Out                As Variant
    Dim lRow                    As Long
    Dim lCol                    As Long

    If Not IsArray(vArr) Then Exit Function
    If Me.DimCounter(vArr) <> 2 Then Exit Function

    If LBound(vArr, 1) = UBound(vArr, 1) Then
        ReDim vArr_Out(LBound(vArr, 2) To UBound(vArr, 2))
        For lCol = LBound(vArr, 2) To UBound(vArr, 2)
            vArr_Out(lCol) = vArr(LBound(vArr, 1), lCol)
        Next lCol
    ElseIf LBound(vArr, 2) = UBound(vArr, 2) Then
        ReDim vArr_Out(LBound(vArr, 1) To UBound(vArr, 1))
        For lRow = LBound(vArr, 1) To UBound(vArr, 1)
            vArr_Out(lRow) = vArr(lRow, LBound(vArr, 2))
        Next lRow
    Else
        Exit Function
    End If

    DimReduce = vArr_Out
End Function