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Matrix Inversion

The inverse of a square matrix is the matrix with the same dimensions that, when
multiplied with the original matrix, gives the Identity Matrix:

If an inverse exists, the original matrix is known as ** invertible**. Otherwise, the orginal
matrix is described as

The Excel MINVERSE function calculates the inverse of a square matrix.

The format of the function is :

MINVERSE( array )

where the array argument is an array of values representing a square matrix (i.e. has the same number of rows as columns).

The resulting inverse matrix has the same number of rows and columns as the original supplied array.

As the Excel Minverse function returns an array of values, the function needs to be entered as an Array Formula.

Array Formulas:

To input an array formula, you need to first highlight the range of cells for the function
result. Type your function into the first cell of the range, and press CTRL-SHIFT-Enter.
Go to the Excel Array Formulas page for more details.

Note that the result from the Minverse function result is calculated to approximately 16 decimal places, so you may get some rounding errors.

In the example below, the Excel Minverse function is used to find the inverse of the 4x4 matrix in cells A1-D4 of the example spreadsheet. The resulting 4x4 matrix is shown in cells F1-I4.

The formula for the function can be seen in the formula bar. The curly braces { } show that the function has been input as an Array Formula.

We can test the Minverse function by multiplying the two matrices in the above spreadsheet, using the Mmult Function. This gives the 4x4 Identity Matrix :

Further information and examples of the Excel Minverse function can be found on the Microsoft Office website.

If you get an error from your Excel Minverse function this is likely to be one of the following :

Common Errors

#VALUE! | - |
Occurs if either: - the supplied array contains a blank or a non-numeric valueor- the supplied array does not have equal numbers of rows and columns |

#NUM! | - | Returned if the supplied matrix is singular - i.e. there is no inverse for the supplied matrix |

#N/A | - |
Occurs in cells outside the range of the resulting matrix. For example, if, in the example above, we had highlighted cells F1-I5 before entering the Minverse function, the 'additional' cells, F5-I5 are not part of the resulting matrix. Therefore, these cells will return the #N/A error. |

Be aware also, that if you don't highlight the full range of cells for the resulting matrix, Excel will just show the part of the result that fits into the highlighted range. There will be no error message to let you know that your highlighted range is not big enough.

This will also be the case if you fail to enter the formula as an array formula - the cell which you enter the formula into will simply show you the first entry of the resulting matrix.