If you spend time with an excellent programmer, one thing that immediately jumps out is how quickly she can write code. It often appears to be magic, the number of keystrokes simply can’t equal the number of characters on the screen. The secret: it doesn’t! Most programmers use ...

R’s model formula infrastructure was discussed in my previous post. Despite the elegance and convenience of the formula method, there are some aspects that are limiting. Limitations to Extensibility The model formula interface does have some limitations: It can be kludgy with many operations on many variables (e.g., ...