Kminit <- 0.2
Vmaxinit <- 0.05
MM.df <- read.csv(file.choose())
plot (MM.df,xlim=c(0,max(MM.df[,1])),ylim=c(0,max(MM.df[,-1])*1.1))
MM.nls <- nls(v ~ (Vmax * S / (Km + S)), data=MM.df, start=list(Km=Kminit, Vmax=Vmaxinit))
Km <- unname(coef(MM.nls)["Km"])
Vmax <- unname(coef(MM.nls)["Vmax"])
curve(Vmax*x/(Km+x),0,max(MM.df$S),add=TRUE)

VmaxKminit <- 0.18
MM2.nls <- nls(v ~ (VmaxKm * S / (1 + S/Km)), data=MM.df, start=list(Km=Kminit, VmaxKm=Vmaxinit))
VmaxKm <- unname(coef(MM2.nls)["VmaxKm"])
mtext(paste(
"Km = ",signif(Km,digits=3),"+/-",signif(summary(MM.nls)$parameters[1,2],digits=3),
", Vmax = ",signif(Vmax,digits=3),"+/-",signif(summary(MM.nls)$parameters[2,2],digits=3),
", Vmax/Km = ",signif(VmaxKm,digits=3),"+/-",signif(summary(MM2.nls)$parameters[2,2],digits=3)))