I am interested in using polymars in R. I will be inputting 10 X variables and my outcome Y variable. I want to make sure my final model includes X1 and any additional variables (X2-X10) chosen with the data adaptive regression technique. Is this possible with polymars? In addition, if I use the step() finction after a lm() function, can I force one variable to be in the final model? I tried using the scope argument in the step() command, but had no luck. I set my upper equal to my full model and was not sure how I tell R that my lower model must have X1 in the model. Thank you in advance, Jenny