# How to compare the fitting of function?

3 messages
Open this post in threaded view
|

## How to compare the fitting of function?

 Hello, I have fitted two curves to the data. How can I tell which one is more fitted? By eye (see plot underneath) I would say that the function Gompertz is better than the function Holling type III; how can I give a number to this hunch? This is an example: ``` # functions holling = function(a, b, x) {   y = (a * x^2) / (b^2 + x^2)   return(y) } gompertz = function(a, b, c, x) {   y = a * exp(-b * exp(-c * x))   return(y) } # data actual <- c(8,  24,  39,  63,  89, 115, 153) holling <- c(4.478803,  17.404533,  37.384128,  62.492663,  90.683630, 120.118174, 149.347683) gompertz <- c(11.30771,  22.39017,  38.99516,  61.19318,  88.23403, 118.77225, 151.19849) # plot plot(1:length(actual), actual, lty = 1 , type = "l", lwd = 2,      xlab = "Index", ylab = "Values") points(1:length(actual), holling, lty = 2, type = "l", col = "red") points(1:length(actual), gompertz, lty = 3, type = "l", col = "blue") legend("bottomright",        legend = c("Actual values", "Holling III", "Gompertz"),        lty = c(1, 2, 3), lwd = c(2, 1,1), col = c("black", "red", "blue")) ``` Thank you ______________________________________________ [hidden email] mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-helpPLEASE do read the posting guide http://www.R-project.org/posting-guide.htmland provide commented, minimal, self-contained, reproducible code.