This is a custom Excel function for regularizing 3D data. It uses the same methodology and arrives at the same results as the spreadsheet that goes with Introduction to Regularizing with 3D Data, but it adds the convenience of a single spreadsheet function that automates the calculation processes without taking up space on your spreadsheet or requiring you to install additional add-ins or DLLs.
The VBA code puts a lot of effort into solving the matrix equations to demonstrate several techniques. For example, it uses a sparse matrix data structure that it reorders by a reverse Cuthill-McKee permutation and solves with a Cholesky decomposition. All calculations are performed in VBA and the example spreadsheet includes full source code. Continue reading