Subtracting two matrices

F

fboehlandt

Active Member
Joined
Sep 9, 2008
Messages
334
Hi everyone,
I need to perform a number of matrix calculations in VBA and intend to use Excel Worksheetfunctions for that. Unfortunately, matrix subtract is only know to .net and excel only knows the following matrix formulas:
.MMULT()
.MINVERSE()
.TRANSPOSE()
.DETERM()
I would like to subtract one matrix from another. My not very elegant workaround is the following:

ReDim subtract(1 To n, 1 To n)
For j = 1 To n
For i = 1 To n
subtract(j, i) = matrix1(j, i) - matrix2(j, i)
Next i
Next j

Both matrices are identical in size (req.) and symmetrical (if it matters). Is there a way of entering a non-descript array formula to calculate the difference of the two matrices?
 

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I'd impliment that code in a function. I'd probably also have the functions Plus and ScalarMult.
 
Upvote 0
The following works but I'm surprised there is no vba functionality for this:
Code: 
Function MSubtract(matrix1, matrix2)
n = UBound(matrix1, 1)
m = UBound(matrix2, 1)
If n <> m Then
    MsgBox ("Input data incompatible")
    Exit Function
End If
ReDim diff(1 To n, 1 To n)
For j = 1 To n
    For i = 1 To n
        diff(j, i) = matrix1(j, i) - matrix2(j, i)
    Next i
Next j
MSubtract = diff
End Function
 
Upvote 0
MMULT etc are spreadsheet functions. On a spreadhseet, formulas like =A1-AA1 dragged, or array formulas like {=A1:E5-AA1:AE5} will do matrix subtraction.

Outside of VB, there is no need for a matrix subtraction function. In VBA for Excel, one can use Excel's spreadsheet funtions for half the job. In VB (no A), all matrix functions are all user written.
 
Upvote 0
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