BERT is a tool for connecting Excel with the statistics language R. Specifically, it's designed to support running R functions from Excel spreadsheet cells. In Excel terms, it's for writing User-Defined Functions (UDFs) in R.
All you have to do is write the function. Everything else – loading the function into Excel, managing parameters, and handling type conversion – is done automatically for you. It really could not be any easier.
BERT also has a console that you can use to control Excel in real time, right from your R code.
Write a function in R, then call it from your Excel spreadsheets. BERT turns R functions into Excel functions automatically. Not only is this the easiest way to write new Excel functions, it lets you use all the power of R in your spreadsheets.
Interact with a spreadsheet in real time using R. Turn Excel into a data store, input system, and report generator for your R code.
If you need to write complex algorithms or do statistical analysis in Excel (or support users who do), BERT is for you. It is possible to write math in VBA – possible – but it's not easy.
BERT makes using R completely transparent in Excel, so you can write complex functions in a real stats language and then plug them directly into Excel. Plus you have access to the entire library of R code and packages already written, tested, and validated by the great community of R users.
Even if you don't write your own code, you can get access to a massive library of helpful functions just by wrapping built-in R functions for things like statistical tests, modeling, classification, and on and on.
For experienced R users, just a heads up: BERT uses its own self-contained environment, and won't have any effect on (or screw up) your existing R setup.