ROC曲线看上去不对

Question

我已经绘制了ROC曲线，使用ROCR软件包，为一个2类问题。根据我的理解，曲线应该看起来像一步一步地改变图形，至少对于较小的数据集是这样。事实上，我的输入很小，但我得到的曲线基本上是直线。是因为PROC符合曲线的一条线，还是因为我错过了其他什么东西？

输入在这里点击我，代码如下所示，最后是ROC部分。感谢你的帮助！

library("caret")
library("ROCR")
sensor6data_s10_2class <- read.csv("/home/sensei/clustering/sensor6data_f21_s10_with2Labels.csv")
sensor6data_s10_2class <- within(sensor6data_s10_2class, Class <- as.factor(Class))
sensor6data_s10_2class$Class2 <- relevel(sensor6data_s10_2class$Class,ref="1")

set.seed("4321")
inTrain_s10_2class <- createDataPartition(y = sensor6data_s10_2class$Class, p = .75, list = FALSE)
training_s10_2class <- sensor6data_s10_2class[inTrain_s10_2class,]
testing_s10_2class <- sensor6data_s10_2class[-inTrain_s10_2class,]
y_s10 <- testing_s10_2class[,22]

ctrl_s10_2class <- trainControl(method = "repeatedcv", number = 10, repeats = 10 , savePredictions = TRUE)
model_train_multinom_s10_2class <- train(Class2 ~ ZCR + Energy + SpectralC + SpectralS + SpectralE + SpectralF + SpectralR + MFCC1 + MFCC2 + MFCC3 + MFCC4 + MFCC5 + MFCC6 + MFCC7 + MFCC8 + MFCC9 + MFCC10 + MFCC11 + MFCC12 + MFCC13, data = training_s10_2class, method="multinom", trControl = ctrl_s10_2class)
pred_multinom_s10_2class = predict(model_train_multinom_s10_2class, newdata=testing_s10_2class)

pred2_s10 <- prediction(as.numeric(as.character(pred_multinom_s10_2class)), as.numeric(as.character(y_s10)))
perf2_s10 <- performance(pred2_s10, "tpr", "fpr")
plot(perf2_s10,col='magenta',lwd=3)

Answer 1

您应该预测类的概率，而不是类标签。试试这个：

pred_multinom_s10_2class = predict(model_train_multinom_s10_2class, newdata=testing_s10_2class, type='prob')

pred2_s10 <- prediction(pred_multinom_s10_2class[,1], as.numeric(as.character(y_s10)))
perf2_s10 <- performance(pred2_s10, "tpr", "fpr")
plot(perf2_s10,col='magenta',lwd=3)

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