[chas]

Excel has the built in MMULT function, but I’m not aware of any built-in support for eigenvalues or eigenvectors. Many people have written such functions though.

That said, I would be surprised if Excel spreadsheets were implemented as matrices. Since you can update one cell and have it automatically update any computation that uses that cell, I would expect spreadsheets to be implemented with some sort of dependency graph so it’s easy to traverse and update the values that need to be changed. (This could be implemented as an adjacency matrix, but I haven’t seen that representation used before for programming language dataflow analysis.)

[galaxyLogic]

Interesting idea. I wonder would it be possible to create a spreadsheet-app where every "sheet" was a matrix and then you would apply linear algebra operations between the sheets to produce output-sheets. Would that be all a spreadsheet-app needs? It might be a simpler unifying design for spreadsheet programming.

The problem I've had with Excel etc. is that every cell can hide an operation and some do and some don't and it becomes difficult to understand what the totality of calculation is. Whereas if it could be expressed as operations between matrices the whole calculation could be expressed as a single formula, perhaps. (?)

[mhh__]

The famous paper "Build systems a la carte" actually describes Excel as a build system for exactly that reason.