I have a data set at hand that I don't know how to analyze it. Essentially, I have four predictors to predict one outcome. For each predictor, the data distribution is different. Two of them look linear, one of them look quadradic, and the other one seems to be at a higher order.
Is there a good tutorial to deal with this kind of situation or multiple nonlinear regression in general? Also, what R commands should I use to analyze this kind of data set?