ConfusionMatrix
image.png
由上表可以計(jì)算的指標(biāo)有：
Accuracy = (TP+TN)/(P+N)
Error Rate = 1 – Accuracy = (FP+FN)/(P+N)
False Positive Rate = Fallout = FP/N
True Positive Rate = Recall = Sensitivity = TP/P
False Negative Rate = Miss = FN/P
True Negative Rate = Specificity = TN/N
Positive Predictive Value = Precision = TP/(TP+FP)
Negative Predictive Value = TN/(TN+FN)
Prediction-conditioned Fallout = FP/(TP+FP)
Prediction-conditioned Miss = FN/(TN+FN)
Rate of Positive Predictions = Detection Prevalence = (TP+FP)/(P+N)
Rate of Negative Predictions = (TN+FN)/(P+N)
Prevalence = (TP+FN)/(P+N)
Detection Rate = TP/(P+N)
Balanced Accuracy = (Sensitivity+Specificity)/2
MCC(Matthews correlation coefficient) = (TPTN - FPFN)/[(TP+FP)(TP+FN)(TN+FP)(TN+FN)]^(1/2)
以ROCR自帶的數(shù)據(jù)集ROCR.simple為例:
require(ROCR)
data(ROCR.simple)
str(ROCR.simple)
## List of 2
## $ predictions: num [1:200] 0.613 0.364 0.432 0.14 0.385 ...
## $ labels : num [1:200] 1 1 0 0 0 1 1 1 1 0 ...
pred.class <- as.integer(ROCR.simple$predictions > 0.5) #這里假設(shè)prediciton>0.5的預(yù)測(cè)為1逃魄，其余為0.
print(cft <- table(pred.class, ROCR.simple$labels)) #先prediction value 后label
## pred.class 0 1
## 0 91 14
## 1 16 79
Method 1: manual
tp <- cft[2, 2]
tn <- cft[1, 1]
fp <- cft[2, 1]
fn <- cft[1, 2]
print(accuracy <- (tp + tn)/(tp + tn + fp + fn))
## [1] 0.85
print(sensitivity <- tp/(tp + fn))
## [1] 0.8494624
print(specificity <- tn/(tn + fp))
## [1] 0.8504673
Method 2: caret
require(caret)
confusionMatrix(cft, positive = "1") #使用上面的table
## Confusion Matrix and Statistics
##
##
## pred.class 0 1
## 0 91 14
## 1 16 79
##
## Accuracy : 0.85
## 95% CI : (0.7928, 0.8965)
## No Information Rate : 0.535
## P-Value [Acc > NIR] : <2e-16
##
## Kappa : 0.6989
##
## Mcnemar's Test P-Value : 0.8551
##
## Sensitivity : 0.8495
## Specificity : 0.8505
## Pos Pred Value : 0.8316
## Neg Pred Value : 0.8667
## Prevalence : 0.4650
## Detection Rate : 0.3950
## Detection Prevalence : 0.4750
## Balanced Accuracy : 0.8500
##
## 'Positive' Class : 1
confusionMatrix(as.factor(pred.class), as.factor(ROCR.simple$labels),
positive = "1", mode = "everything")
## Confusion Matrix and Statistics
##
## Reference
## Prediction 0 1
## 0 91 14
## 1 16 79
##
## Accuracy : 0.85
## 95% CI : (0.7928, 0.8965)
## No Information Rate : 0.535
## P-Value [Acc > NIR] : <2e-16
##
## Kappa : 0.6989
##
## Mcnemar's Test P-Value : 0.8551
##
## Sensitivity : 0.8495
## Specificity : 0.8505
## Pos Pred Value : 0.8316
## Neg Pred Value : 0.8667
## Precision : 0.8316
## Recall : 0.8495
## F1 : 0.8404
## Prevalence : 0.4650
## Detection Rate : 0.3950
## Detection Prevalence : 0.4750
## Balanced Accuracy : 0.8500
##
## 'Positive' Class : 1
參考資料：
