I have empirical Bayes estimates for slopes and intercepts for a number of subjects and I would like to plot the slopes and intercepts with confidence ellipses. These ellipses would be based on the confidence intervals for the slope and intercepts (forming the major and minor axis of each ellipse), and the correlation in the slope and intercepts.
The ellipse function in the car library looks like the way to go, the add= argument would allow me to over-plot. There are three arguments that generate the ellipse. center shape radius Center would be the posterior means for the intercept and slopes. shape would be the posterior covariance matrices (I think) I don't know what I would use for the radius argument however. My guess would be the upper bound of a confidence interval for either the slope or the intercept, but this does not return sensible results. I guess I need to know more about the geometry of ellipse, but if anybody can provide any assistance, I would really appreciate it. thanks! -- ********Note the new contact information******* Samuel H. Field, Ph.D. Senior Research Investigator CHERP/Division of Internal Medicine - University of Pennsylvania Philadelphia VA Medical Center 3900 Woodland Ave (9 East) Philadelphia, PA 19104 (215) 823-5800 EXT. 6155 (Office) (215) 823-6330 (Fax) ______________________________________________ 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.
