keras 自定義 metrics
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自定義 Metrics
在 keras 中操作的均為 Tensor 對象，因此，需要定義操作 Tensor 的函數來操作所有輸出結果，定義好函數之后，直接將其放在 model.compile 函數 metrics 中即可生效：
def precision(y_true, y_pred): # Calculates the precision true_positives = K.sum(K.round(K.clip(y_true * y_pred, 0, 1))) predicted_positives = K.sum(K.round(K.clip(y_pred, 0, 1))) precision = true_positives / (predicted_positives + K.epsilon()) return precision def recall(y_true, y_pred): # Calculates the recall true_positives = K.sum(K.round(K.clip(y_true * y_pred, 0, 1))) possible_positives = K.sum(K.round(K.clip(y_true, 0, 1))) recall = true_positives / (possible_positives + K.epsilon()) return recall def fbeta_score(y_true, y_pred, beta=1): # Calculates the F score, the weighted harmonic mean of precision and recall. if beta < 0: raise ValueError('The lowest choosable beta is zero (only precision).') # If there are no true positives, fix the F score at 0 like sklearn. if K.sum(K.round(K.clip(y_true, 0, 1))) == 0: return 0 p = precision(y_true, y_pred) r = recall(y_true, y_pred) bb = beta ** 2 fbeta_score = (1 + bb) * (p * r) / (bb * p + r + K.epsilon()) return fbeta_score def fmeasure(y_true, y_pred): # Calculates the f-measure, the harmonic mean of precision and recall. return fbeta_score(y_true, y_pred, beta=1) 使用方法如下：
model.compile(
optimizer=Adam(),
loss='binary_crossentropy', metrics = ['accuracy', fmeasure, recall, precision])