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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