My script fits a third-order polynomial to my data with something like this:
model <- lm( y ~ poly(x, 3) ) What I'd like to do is find the theoretical maximum of the polynomial (i.e. the x at which "model" predicts the highest y). Specifically, I'd like to predict the maximum between 0 <= x <= 1. What's the best way to accomplish that in R? Bonus question: can R give me the derivative or 2nd derivative of the polynomial? I'd like to be able to compute these at that maximum point. Thanks in advance! // joseph w. clark , phd , visiting research associate \\ university of nebraska at omaha - college of IS&T ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.