I have measured growth rates over a range of temperatures (temperature response curve) and would like to fit an already established equation/model to it. I'm very new to R and have trouble coding it right. This is my data: x <- c(37.8, 34.8, 32.25, 29.65, 26.75, 24.4, 21.45, 19.15, 16.2, 13.7, 10.95, 8.2, 5.4) y <- c(0.0381, 0.018133333, 1.057033333, 2.3395, 2.5188, 2.6132, 2.398466667, 2.082966667, 1.687366667, 1.389233333, 0.9835, 0.639833333, 0.3757) The equation I'm trying to fit is as follows: $y=(3.5-x/10)(x/25)^{(5/2)}$ I tried modifing code that I found here to my equation but have been unsuccessful so far. Can someone help with this with a step by step guide for dummies? Updated model for my dataset: nls(y~((Tmax-x)/(Tmax-Topt))*(((x/Topt)^((Topt/(Tmax-Topt)))))