将MMult的结果赋给数组变量时键入mimsatch

Question

Apologies for the newbie question, but I couldn't find an answer when searching.

I'm fairly new to matrix manipulation in VBA. I keep on getting a type mismatch with the following code.

Sub matrixtest()

Dim matrix1() As Integer
Dim matrix2() As Integer
Dim matrix3() As Integer
Dim i, j, k As Integer

'populate matrix1
ReDim matrix1(3, 3)
For j = 1 To 3
    For i = 1 To 3
        matrix1(i, j) = Range("C5").Offset(i - 1, j - 1)
    Next i
Next j

'populate matrix2
ReDim matrix2(3, 3)
For j = 1 To 3
    For i = 1 To 3
        matrix2(i, j) = Range("G5").Offset(i - 1, j - 1)
    Next i
Next j

ReDim matrix3(3, 3)
matrix3 = Application.WorksheetFunction.MMult(matrix1, matrix2)

End Sub

Answer 1

If you replace the line

matrix3 = Application.WorksheetFunction.MMult(matrix1, matrix2)

By

Debug.Print TypeName(matrix3 = Application.WorksheetFunction.MMult(matrix1, matrix2))

The output is:

Variant()

Which can't be assigned to an Integer() .

I would recommend replacing

Dim matrix1() As Integer
Dim matrix2() As Integer
Dim matrix3() As Integer
Dim i, j, k As Integer

by

Dim matrix1, matrix2, matrix3 As Variant 'note lack of ()
Dim i, j, k As Long 'Integer is borderline obsolete in VBA

Variants do a nice job of holding and passing arrays and tend to handle any needed type conversions automatically. When dealing with arrays in VBA, I tend to use them almost exclusively. For one thing, it makes it easy to load arrays from ranges.

Just use ReDim to make the variants hold arrays:

ReDim matrix1(1 to 3, 1 to 3) 'doesn't hurt to be explicit about lower bounds
ReDim matrix2(1 to 3, 1 to 3)
'load arrays...
'no need to redim matrix3, just:
matrix3 = Application.WorksheetFunction.MMult(matrix1, matrix2)

There is an even shorter way of doing what you are trying to do:

matrix1 = Range("C5:E7").Value
matrix2 = Range("G5:I7").Value
matrix3 = Application.WorksheetFunction.MMult(matrix1, matrix2)

In the above code you don't need to use any preliminary ReDim . When you want to load the values of a rectangular range into a variant in VBA, you don't need to loop, which is needlessly slow. Just assign the values in one fell swoop.