> Is the "probability of the true label" the best prediction to feed to > the ROCR package, or is it better to use the "decision.value"
Since AFAIK they are related by a monotonous transformation, both approaches should lead to the same ROC curve, shouldn't they? (not tested) On Tue, Aug 4, 2009 at 8:14 PM, Noah Silverman<n...@smartmediacorp.com> wrote: > Good point. I'm not sure how I missed that. > > This does lead to an additional question: > > Is the "probability of the true label" the best prediction to feed to > the ROCR package, or is it better to use the "decision.value" > > Anybody have any experience on this one? > > Thanks! > > -N > > On 8/4/09 3:28 AM, Christian Schulz wrote: >> Hi, >> >> you need the score value , have a look at ?svm.predict and in the >> ROCR example. >> >> traindata <- as.data.frame(matrix(runif(1000),ncol=10)) >> trainlabels <- >> as.factor(sample(c("win","lose"),nrow(data),replace=T,prob=c(0.5,0.5))) >> >> model <- svm(traindata,trainlabels, type="C-classification", >> kernel="radial", cost=10, >> class.weights=c("win"=3,"lose"=1), scale=FALSE, probability = TRUE) >> >> prediction <- predict(model, traindata, decision.values = TRUE, >> probability = TRUE) >> probs <- attr(prediction, "probabilities")[,1] >> pred <- prediction(probs,trainlabels) >> >> HTH Christian >> >>> Hello, >>> >>> I've come across a strange error... >>> >>> >>> Here is what happens: >>> >>> model <- svm(traindata,trainlabels, type="C-classification", >>> kernel="radial", cost=10, class.weights=c("win"=3,"lose"=1), >>> scale=FALSE, probability = TRUE) >>> predictions <- predict(model, traindata) >>> pred <- prediction(predictions, trainlabels) >>> >>> >>> This returns an error: >>> Error in prediction(predictions, trainlabels) : >>> Format of predictions is invalid. >>> >>> Yet my predictions is just a matrix of predicted labels. Nothing >>> fancy. (In fact, my step follow the exact example on the ROCR >>> homepage.) >>> >>> A search through google for "Format of predictions is invalid" >>> returns zero results. >>> >>> Can anyone suggest how I might fix this problem? >>> >>> Thank You, >>> >>> >>> >>> >>> >>> [[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. > ______________________________________________ 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.