Array multiplication and matrix inversion with VBA

I am trying to do some calculations with arrays.

e.g. I want to solve Ax=y, so I use the开发者_StackOverflow following code to do so, where A is a square matrix and y is a col. vector. In VBA, A is an array with two dimension and y is one with one dimension. However, this code does not work...

x = WorksheetFunction.MMult(WorksheetFunction.MInverse(A), y)

Where did I get wrong? Thanks!

You can be committing one or more of many mistakes:

• Arrays not defined as Variant (Most worksheetfunctions won't work if data type is something other than Variant).
• Dimensions of A and y don't match up as they need to for matrix multiplication.
• In particular, won't work if y size is (1,2) instead of (2,1) as in example below.
• etc... Can be anything, really. You don't tell us what error message you get.

Here's an example that works:

Dim A As Variant
Dim y As Variant
Dim x As Variant

ReDim y(1 To 2, 1 To 1)
y(1, 1) = 2
y(2, 1) = 3

ReDim A(1 To 2, 1 To 2)
A(1, 1) = 3
A(2, 1) = 1
A(1, 2) = 4
A(2, 2) = 2

x = WorksheetFunction.MMult(WorksheetFunction.MInverse(A), y)

Let matrix A (3 x 3) be an array in Range("A1:C3"), matrix y (3 x 1) be an array in Range("E1:E3"), and matrix x (3 x 1) be an array in Range("G1:G3"). Then you can try this simple program:

Range("G1:G3") = WorksheetFunction.MMult(WorksheetFunction.MInverse(Range("A1:C3")), Range("E1:E3"))

By using the same procedure, you can do this to find the result of multiplication of a matrix (n x m) with a matrix (p x q). Of course for the simplification you should declare the variables first. I hope this answer can help you.