hi, I am sure this is an obvious question, I have a optimized model with coefficients from stepAIC. I can't figure out how to find the max value of a function with those coefficients. Its part of a dynamic web page or else i would have done it by hand. The code works fine, so you probably don't need it, but here it is: library(MASS) dd<-read.csv("Guest.dat", header = TRUE, sep = "," ) res <- stepAIC(glm(Yield ~ (1 + NTP + DNA + T7pol)^2 , data=dd ), list(upper = Yield ~ (1 + NTP + DNA + T7pol )^2 , lower = Yield ~ 1 ) , trace=0 ) coef(res) (Intercept) NTP DNA T7pol DNA:T7pol 1776 -19 -8.64 -10 1.5 I need the function back out y = 1776 - 19*NTP -8.64*DNA -10*T7pol + 1.5 *DNA*T7pol in order to send it to optim() or some optimizer thanks ld