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 <ligges@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
>>
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>>
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