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ROC Curve and AUC

ROC Curve (Receiver Operating Characteristics Curve) and AUC (Area Under the Receiver Operating Characteristics Curve) are the tools to evaluate Pattern Recognition with Confusion Matrix .

They are used if we think, "At first, TP is maximized. Second, FP is minimized."

Relationship among Threshold, FP ratio and TP ratio

FP ratio and TP ratio are
FP = (FP + TN)
TP = (TP + FN)

confusion matrix

Examples TP ratio and FP ratio for threshold 3 and 7.
TP ratio and FP ratio

When threshold is 3, TP ratio is 1.

When threshold is 7, FP ratio is 0.

More examples is belos.
TP ratio and FP ratio

Purpose to Use TP ratio and FP ratio

Histgram is useful to understand the meaning that "threshold is the best".
TP ratio and FP ratio

ROC Curve

Scatter plot of TP ratio and FP ratio is called "ROC Curve".
ROC Curve

ROC Curve for Perfect Pattern Recognition

If we get ROC Curve like below, we can get perfect pattern recognition system.
ROC Curve ROC Curve ROC Curve ROC Curve

AUC

When ROC Curve is the perfect pattern, Area under the curve is 1.

The are is used to evaluate the level of pattern recoginition. It is called "AUC".

AUC is from 0 to 1.




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