Mark Seeto wrote: > > > garciap wrote: >> >> Hi to all the people, >> >> I'm having a trouble when trying to plot a quadratic function. I have the >> code: >> >> regression<-nls(Survival~beta1+beta2*PI+beta3*PI^2, data=cubs, >> start=list(beta1 = 1, beta2 = 1, beta3 = 1)) >> plot(Survival~PI,data=cubs, ylab="Survival", xlab="PI") >> lines(cubs$PI, fitted(regression)) >> >> but the plotted line is not the quadratic one, rather it appears a number >> of lines whose meaning I do not know. It seems to be an stupid trouble, >> but I tried a number of alternatives and nothing works. >> >> Regards, >> >> pablo >> > > The problem could be that cubs$PI is not sorted. You could try > > plot(Survival~PI,data=cubs, ylab="Survival", xlab="PI") > lines(sort(PI), fitted(regression)[order(cubs$PI)]) > > Also, you could use linear regression with lm instead of using nls. > > Regards, > Mark >
Sorry, that should have been plot(Survival~PI,data=cubs, ylab="Survival", xlab="PI") lines(sort(cubs$PI), fitted(regression)[order(cubs$PI)]) -- View this message in context: http://r.789695.n4.nabble.com/a-question-on-plotting-nonlinear-regression-tp3690828p3691169.html Sent from the R help mailing list archive at Nabble.com. ______________________________________________ [email protected] 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.
