我在R中创建了一个决策树模型。目标变量是薪资，我们试图根据其他输入变量预测一个人的薪资是否高于或低于50k

df<-salary.data train = sample(1:nrow(df), nrow(df)/2)train = sample(1:nrow(df), size=0.2*nrow(df))test = - traintraining_data = df[train, ]testing_data = df[test, ]fit <- rpart(training_data$INCOME ~ ., method="class", data=training_data)##generate treetesting_data$predictionsOutput = predict(fit, newdata=testing_data, type="class")##make prediction

之后我尝试通过以下方式创建增益图

# Gain Chartpred <- prediction(testing_data$predictionsOutput, testing_data$INCOME)gain <- performance(pred,"tpr","fpr")plot(gain, col="orange", lwd=2)

通过参考资料，我无法理解如何使用ROCR包通过’Prediction’函数构建图表。这仅适用于二元目标变量吗？我收到错误信息说’预测格式无效’

任何帮助都将非常感激，以帮助我为上述模型构建增益图。谢谢！！

  AGE          EMPLOYER     DEGREE             MSTATUS            JOBTYPE     SEX C.GAIN C.LOSS HOURS1  39         State-gov  Bachelors       Never-married       Adm-clerical    Male   2174      0    402  50  Self-emp-not-inc  Bachelors  Married-civ-spouse    Exec-managerial    Male      0      0    133  38           Private    HS-grad            Divorced  Handlers-cleaners    Male      0      0    40         COUNTRY INCOME1  United-States  <=50K2  United-States  <=50K3  United-States  <=50K

回答：

将预测转换为向量，使用c()

library('rpart')library('ROCR')setwd('C:\\Users\\John\\Google Drive\\working\\R\\questions')df<-read.csv(file='salary-class.csv',header=TRUE)train = sample(1:nrow(df), nrow(df)/2)train = sample(1:nrow(df), size=0.2*nrow(df))test = - traintraining_data = df[train, ]testing_data = df[test, ]fit <- rpart(training_data$INCOME ~ ., method="class", data=training_data)##generate treetesting_data$predictionsOutput = predict(fit,                                          newdata=testing_data, type="class")##make prediction# Doesn't work# pred <- prediction(testing_data$predictionsOutput, testing_data$INCOME)v <- c(pred = testing_data$predictionsOutput)pred <- prediction(v, testing_data$INCOME)gain <- performance(pred,"tpr","fpr")plot(gain, col="orange", lwd=2)