You can access the data directly by using something like perf@x.values[[1]]. Not sure if that helps you. The package pROC allows you to do partial areas under the curve by selecting a range of specificity or sensitivity that you're interested in.
On Tue, May 28, 2013 at 2:17 AM, Guido Leoni <guido.le...@gmail.com> wrote: > Ye sorry > of course i'm interested to the area ranging from 0;0 to 0.4;0.8 > thank you > Guido > > > 2013/5/27 Uwe Ligges <lig...@statistik.tu-dortmund.de> > > > > > > > On 27.05.2013 16:18, Guido Leoni wrote: > > > >> Dear list > >> I'm testing a predictor and I produced nice performance plots with ROCR > >> package utilizing the 3 standard command > >> > >> pred <- prediction(predictions, labels) > >> perf <- performance(pred, measure = "tpr", x.measure = "fpr") > >> plot(perf, col=rainbow(10)) > >> > >> The pred object and the perfo object are S4 > >> with the following slots > >> > >> An object of class "performance" > >> Slot "x.name": > >> [1] "False positive rate" > >> > >> Slot "y.name": > >> [1] "True positive rate" > >> > >> Slot "alpha.name": > >> [1] "Cutoff" > >> > >> Slot "x.values": > >> [[1]] > >> [1] 0.00 0.00 0.05 0.10 0.10 0.10 0.10 0.10 0.15 0.15 0.15 0.20 0.25 > >> 0.25 > >> 0.25 0.25 0.25 0.30 0.35 0.35 0.35 0.40 0.40 0.45 0.50 0.50 0.55 0.55 > 0.60 > >> [30] 0.65 0.65 0.70 0.70 0.75 0.80 0.85 0.90 0.90 0.95 1.00 1.00 > >> > >> > >> Slot "y.values": > >> [[1]] > >> [1] 0.00 0.05 0.05 0.05 0.10 0.15 0.20 0.25 0.25 0.30 0.35 0.35 0.35 > >> 0.40 > >> 0.45 0.50 0.55 0.55 0.55 0.60 0.65 0.65 0.70 0.70 0.70 0.75 0.75 0.80 > 0.80 > >> [30] 0.80 0.85 0.85 0.90 0.90 0.90 0.90 0.90 0.95 0.95 0.95 1.00 > >> > >> > >> Slot "alpha.values": > >> [[1]] > >> [1] Inf 33309 32968 31688 31648 31355 31122 31047 30777 30589 30460 > >> 30395 30305 30159 29841 29101 28734 28657 28393 28196 27740 27662 27373 > >> 27078 > >> [25] 26763 26303 25573 25416 25364 25357 24993 23834 23789 23616 22357 > >> 20669 20092 18720 18136 17323 16665 > >> > >> > >> Now i'd like to make a plot (and also compute the AUC) only of the area > >> corresponding to 0.80 y.values and 0.40 x.values. > >> According to your experience is it possible to subset the perf object to > >> the afore mentioned values? > >> > > > > But x=0.4 and y=0.8 is just a point, so I don't get which plot and area > > you are talking about now? > > > > Best, > > UWe Ligges > > > > > > > > > > > > > > Thanks > >> Guido > >> > >> [[alternative HTML version deleted]] > >> > >> ______________________________**________________ > >> R-help@r-project.org mailing list > >> https://stat.ethz.ch/mailman/**listinfo/r-help< > https://stat.ethz.ch/mailman/listinfo/r-help> > >> PLEASE do read the posting guide http://www.R-project.org/** > >> posting-guide.html <http://www.R-project.org/posting-guide.html> > >> and provide commented, minimal, self-contained, reproducible code. > >> > >> > > [[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. > [[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.
