Error:attempt to apply non-function
You’re missing *s in the last two terms of your expression, so R is interpreting (e.g.) 0.207 (log(DIAM93))^2 as an attempt to call a function named 0.207 … For example: Error: attempt to apply non-function Your (unreproducible) expression should read: Mathematica is the only computer system I know of that allows juxtaposition to be used for multiplication …