There are point in polygon functions in some of the spatial packages that would tell you if a point is within a polynomial approximation of the ellipse. But in your case I would take a different approach. Generally confidence ellipses are based on manhalobis distances, so you can just compute the manhalobis distance of the point relative to the mean vector (taking the appropriate covariance matrix into account), then if that distance is above a certain value it is outside the ellipse, if less it is inside.
-----Original Message----- From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] On Behalf Of Jessica Minkue Sent: Saturday, May 28, 2011 11:45 AM To: r-help@r-project.org Subject: [R] Observation in a confidence ellipse Hello everyone I really need some help here. I made a confidence ellipse using the function ellipse from the package ellipse: ellipse(SD, centre=colMeans(pcsref),t=sqrt((p * (n-1)/(n-p))*qf(0.99, p,n-p)) Now, I want to write a function whom return TRUE or FALSE if a given observation is in the confidence ellipse. But I have no clue how to do it Can anyone help me? Best regards Jessica [[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. ______________________________________________ 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.
