Alright, I apologize for this basic question - I am both an R and loess noob. I am trying to predict the values of column Y in data1 (100000x18 entries) using a loess fit on training (500x18 entries) and columns A B and C. (training are not members of data1) fit <- loess(Y ~ A + B + C, training) predicted <- predict(fit, data1) However, I'm getting such good predictions that I have to assume that I am not using these functions correctly and/or don't understand loess. One explanation would be that predict(fit, data1) is actually using info from data1 to refit the loess model. Any clues would be appreciated as I try to figure this out. [[alternative HTML version deleted]]