Matrix inversion - size of Matrix

[Iceman]

I've found through a brief trial and error that the largest matrix I can invert (Excel:mac, by the way) is 49x49.

I would like to invert larger matrices (very useful for engineering problems like finite difference thermal modelling, where the matrix size limits how complicated a model you can build) and wondered if this is a hard limit, is machine specific or whatever?

Many thanks

 

[Aladin Akyurek]

On 2002-11-16 13:45, Iceman wrote:
I've found through a brief trial and error that the largest matrix I can invert (Excel:mac, by the way) is 49x49.

I would like to invert larger matrices (very useful for engineering problems like finite difference thermal modelling, where the matrix size limits how complicated a model you can build) and wondered if this is a hard limit, is machine specific or whatever?

Many thanks

If you have access to a Windows machine, you could use the morefunc.xll add-in which has extended matrix functions, e.g., MINVERSE.EXT for 256x256.

 

[tusharm]

morefunc is by Laurent Longre and is available from http://longre.free.fr/english/

 

[kelvin]

Merci M. laurent - les adjonctions sont perfect!

***

While the MINVERSE.EXT worked for my application (I was unable to invert beyond 51x51), the function is limited to 256 columns in width (the natural limit of the sheet obviously) and so, 256 rows in depth as well.

If you really need to invert larger forms, one could always try partitioning the larger matrix into smaller sub-matrices.

See this link for a "quick and dirty" review of inverting partitioned matrices:

http://www.cc.utah.edu/~nahaj/math/matrix.inverse.notes.html

Note:

A is m x m,
B is m x n,
C is n x m, and
D is n x n

only the A and D partitions need be inverted and are presumeably of managable size.

****

Here's another question though... When will Excel expand beyond the current 256 column limitation? It seems to me that today's computers could handle much more than that (say Column ZZ ---> 676 columns) even if we had to sacrifice some of the thousands of rows that I only use rarely.

 

[Aladin Akyurek]

...Here's another question though... When will Excel expand beyond the current 256 column limitation? It seems to me that today's computers could handle much more than that (say Column ZZ ---> 676 columns) even if we had to sacrifice some of the thousands of rows that I only use rarely.

Looking at it from a database angle, having 256 fields should be adequate.