Strange error with ROCR

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,





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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"

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]]

? ? ? ?[[alternative HTML version deleted]]