Find Matrix Inverse for 2*2 and 3*3 matrices

I am writing a VBA function (of type Variant) to calculate the
inverse of an arbitrary 2*2 or 3*3 matrix in Excel. I am using the formula involving the adjoint
of the matrix. I need to have my function to flag unsuitable matrices (i.e., not 2 * 2 or 3 * 3) with a message box and then stop. To further clarify the adjoint of the matrix:
Step 1: calculating the Matrix of Minors,
Step 2: then turn that into the Matrix of Cofactors,
Step 3: then the Adjugate, and
Step 4: multiply that by 1/Determinant.

This is the code I have written so far but I am having a problem implementing the code to calculate the matrix cofactors and the matrix of minors. I am also not sure whether the code I have written for transpose and the determinant are correct. My main issue is figuring out how to successfully access the cell elements and multiply/add/subtract them. Thanks for any help in advance.

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How is this thread any different from your other thread here?
https://www.excelforum.com/excel-pro...functions.html

It is an interesting programming exercise, but is there some reason you are not just using the built in MINVERSE() function https://support.office.com/en-us/art...9-59da2d72efc6 Recall that you can call Excel's built in functions from VBA: https://docs.microsoft.com/en-us/pre...1(v=office.14) Unless there is some reason (such as an educational exercise), it seems to me that this will be easiest to just use Excel's built in function.

Please do NOT delete posts, even if the thread is duplicate.

here is the original post #1...

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I am writing a VBA function (of type Variant) to calculate the
inverse of an arbitrary 2*2 or 3*3 matrix in Excel. I am using the formula involving the adjoint
of the matrix. I need to have my function to flag unsuitable matrices (i.e., not 2 * 2 or 3 * 3) with a message box and then stop. To further clarify the adjoint of the matrix:
Step 1: calculating the Matrix of Minors,
Step 2: then turn that into the Matrix of Cofactors,
Step 3: then the Adjugate, and
Step 4: multiply that by 1/Determinant.

This is the code I have written so far but I am having a problem implementing the code to calculate the matrix cofactors and the matrix of minors. I am also not sure whether the code I have written for transpose and the determinant are correct. My main issue is figuring out how to successfully access the cell elements and multiply/add/subtract them. Thanks for any help in advance.

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I've reinstated the opening post. The OP was not particularly happy about my reconciling his three threads on this issue.

I'm not sure how best torespond. As an educational exercise, I would not want to just give answers, as I believe you will learn more discovering answers on your own. A few comments that I hope will help without interfering with what you are supposed to be learning:

I need to have my function to flag unsuitable matrices (i.e., not 2 * 2 or 3 * 3) with a message box and then stop.

This comment depends a lot on how you intend to use this function. When I started creating User-Defined functions (UDFs) intended to be called from a spreadsheet, I learned very quickly that I did not want a UDF to use an input box or a message box. When the error condition exists, you will get the message box (and need to dismiss the message box) for each and every calculation event (and for every copy of the function in the spreadsheet, if you have more than one copy). It should not take much imagination to see that this will likely become very irritating very quickly. Just want to suggest that you consider how you intend to use the function so you know how you want the function to interact with the user.

My main issue is figuring out how to successfully access the cell elements and multiply/add/subtract them.

Since r is a range object, I would suggest referencing MSFT's help file for the range object: https://msdn.microsoft.com/en-us/vba...e-object-excel -- in particular, note the similarities and differences between the .cells() method and the .range() method. As a quick test procedure, I wrote this simple procedure

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I might suggest running this simple procedure with different ranges past to the function and see what each debug.print statement outputs. Modify the code to test accessing different cells in the range. This and the help file should give you some good idea of how to access the different cells in the range.

Does that help? Do you have additional questions?

Originally Posted by AliGW

I've reinstated the opening post. The OP was not particularly happy about my reconciling his three threads on this issue.

OH well. They would either be merged, or closed.

I can not seem to think of a way to use .range instead of .cell.

Is it necessary to use the .Range method? The idea behind the different methods is to choose the one that is easiest to use/program. If .Cells() is easier than .Range(), there should be no need to use .Range() -- Unless, again, this is an educational exercise to practice using the different methods.

can I store the values of each cell then retrieve those in an array?

If I understand the question -- yes, you can take r and store it in a VBA array. See tutorial here: http://www.cpearson.com/Excel/ArraysAndRanges.aspx One thing I would note is that, if these are UDFs intended to be called from the spreadsheet, you will assign the result array to the function name which is how the array will get output to the spreadsheet.