Here is a clean version. I did this with nls and it works (see below), but I need to do it with optim. Keun-Hyung
# optim vol<-rep(c(0.03, 0.5, 2, 4, 8, 16, 32), 3) time<-rep(c(2,4,8),each=7) p.mated<-c(0.47, 0.48, 0.43, 0.43, 0.26, 0.23, NA, 0.68, 0.62, 0.64, 0.58, 0.53, 0.47, 0.24, 0.8, 0.79, 0.71, 0.56, 0.74, 0.8, 0.47) eury<-data.frame(vol=vol, time=time, p.mated=p.mated) eury<-na.omit(eury); eury p0<- c(f=0.87, b=0.1, d=10) eury.fit <- function (f, time, vol) { f<-p[1]; b<-p[2]; d<-p[3] p.mated = p[1] * ( (1 - exp(-p[2]*time))-(p[2]/(p[2]-(p[3]/vol))) * (exp(-p[3]/vol*time)-exp(-p[2]*time))) } eury.opt<- optim(p0, fn=eury.fit, NULL, method = "BFGS", hessian = TRUE) # I received the following error message. Error in fn(par, ...) : argument "time" is missing, with no default ## done with nls - this works eury.newfit1 <- nls(p.mated ~ f * ( 1 - exp(-b*time)-(b/(b-d/vol))*(exp(-d/vol*time)-exp(-b*time))), data=eury, start=list(f=.87, b=0.1, d=10)) v <- log10(range(eury$vol)) y <- expand.grid(vol=10^seq(min(v), max(v), length=100), time=c(2,4,8)) y$pred.mate.new <- predict(eury.newfit1,y) plot (eury$vol, eury$p.mated, type="n", log="x", xlab="Volume L", ylab = "Fraction Mating") for (i in c(2, 4, 8)) { points(eury$vol[eury$time==i], eury$p.mated[eury$time==i], pch=16, col=(i/2)+1) lines(y$vol[y$time==i], y$pred.mate.new[y$time==i], lwd=3, col=i) } legend(.005,.2, c(" 2h","4h","8h"), col=c(2,4,8), lwd=3) [[alternative HTML version deleted]] ______________________________________________ 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.