> -----Original Message----- > From: r-help-boun...@r-project.org > [mailto:r-help-boun...@r-project.org] On Behalf Of olivier.abz > Sent: Thursday, October 22, 2009 7:23 AM > To: r-help@r-project.org > Subject: [R] How to calculate the area under the curve > > > Hi all, > > I would like to calculate the area under the ROC curve for my > predictive > model. I have managed to plot points giving me the ROC curve.
If x and y are the coordinates of the edges of the polygon (e.g., polygon(x,y) would draw the polygon) then the polygon's signed area is given by the following area<-function(x,y)sum(x*c(y[-1],y[1]) - c(x[-1],x[1])*y)/2 (Positive if edge is traced counter-clockwise.) This is a discrete version of Green's theorem. Bill Dunlap Spotfire, TIBCO Software wdunlap tibco.com > However, I do > not know how to get the value of the area under. > Does anybody know of a function that would give the result I > want using an > array of specificity and an array of sensitivity as input? > > Thanks, > > Olivier > -- > View this message in context: > http://www.nabble.com/How-to-calculate-the-area-under-the-curv e-tp26010501p26010501.html > Sent from the R help mailing list archive at Nabble.com. > > ______________________________________________ > 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.