I hadn't thought of that. I'll run some tests...
-N
On 8/4/09 11:49 AM, Tobias Sing wrote:
>> 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]]
>>>>
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>>>>
>>>>
>>>
>> [[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.
>>
>>
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