One idea of problem solving is, or should be, I think, that one should tackle problems of high complexity, but not too high. That sounds trivial, cooler tone would be “as hard as possible, as easy as necessary” which is basically the same thing. In software development including Rstats, a similar principle applies. Sounds theoretical, I admit. So see here some lines of code that has bitten me recently: obs <- c(1,2,3) pred <- c(1,2,4) monster <- 1 - (sum((obs - pred)^2))/(sum((obs - mean(obs))^2)) monster ## [1] …