[R] Strange error with ROCR

[Christian Schulz]

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,
>
>
>
>
>
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>
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