Hello, SAS' point and click interface has the option of produce a scatterplot with a superimposed confidence ellipse for the correlation coefficient. Since I generally like R so much better, I would like to reproduce this in R. I've been playing with the ellipse package. In order to have the points and the ellipse on the same graph I've done the following. (Load ellipse package...) > data(Puromycin) > attach(Puromycin) > my<-mean(rate) > mx<-mean(conc) > sdy<-sd(rate) > sdx<-sd(conc) > r<-cor(conc,rate) > plot(ellipse(r,scale=c(sdx,sdy),centre=c(mx,my)),type='l') > points(conc,rate)
1) Is my use of 'scale' and 'centre' theoretically correct? 2) Is there a more efficient way to get the 5 parameters? (I guess I could write a little function, but has it already been done?) The non-linear relationship between these variables brings up another point: Is there a way to plot a contour (empirical?) containing, say, 95% of the values. Thanks for your time! Tanya ______________________________________________ [EMAIL PROTECTED] mailing list https://www.stat.math.ethz.ch/mailman/listinfo/r-help
