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July 19, 2018 00:02
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Keras Stateful Custom Metric Recall
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class Recall(keras.layers.Layer): | |
"""Stateful Metric to count the total recall over all batches. | |
Assumes predictions and targets of shape `(samples, 1)`. | |
# Arguments | |
name: String, name for the metric. | |
""" | |
def __init__(self, name='recall', **kwargs): | |
super(Recall, self).__init__(name=name, **kwargs) | |
self.stateful = True | |
self.recall = K.variable(value=0.0, dtype='float32') | |
self.true_positives = K.variable(value=0, dtype='int32') | |
self.false_negatives = K.variable(value=0, dtype='int32') | |
def reset_states(self): | |
K.set_value(self.recall, 0.0) | |
K.set_value(self.true_positives, 0) | |
K.set_value(self.false_negatives, 0) | |
def __call__(self, y_true, y_pred): | |
"""Computes the number of true positives in a batch. | |
# Arguments | |
y_true: Tensor, batch_wise labels | |
y_pred: Tensor, batch_wise predictions | |
# Returns | |
The total number of true positives seen this epoch at the | |
completion of the batch. | |
""" | |
y_true = K.cast(y_true, 'int32') | |
y_pred = K.cast(K.round(y_pred), 'int32') | |
# False negative calculations | |
y_true = K.cast(y_true, 'int32') | |
y_pred = K.cast(K.round(y_pred), 'int32') | |
false_neg = K.cast(K.sum(K.cast(K.greater(y_pred, y_true), 'int32')), 'int32') | |
current_false_neg = self.false_negatives * 1 | |
self.add_update(K.update_add(self.false_negatives, | |
false_neg), | |
inputs=[y_true, y_pred]) | |
# True positive calculations | |
correct_preds = K.cast(K.equal(y_pred, y_true), 'int32') | |
true_pos = K.cast(K.sum(correct_preds * y_true), 'int32') | |
current_true_pos = self.true_positives * 1 | |
self.add_update(K.update_add(self.true_positives, | |
true_pos), | |
inputs=[y_true, y_pred]) | |
# Combine | |
recall = (K.cast(self.true_positives, 'float32') / (K.cast(self.true_positives, 'float32') + K.cast(self.false_negatives, 'float32') + K.cast(K.epsilon(), 'float32'))) | |
self.add_update(K.update(self.recall, | |
recall), | |
inputs=[y_true, y_pred]) | |
return recall |
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Shouldn't false negative be where y_true > y_pred? Hence:
false_neg = K.cast(K.sum(K.cast(K.greater(y_true, y_pred), 'int32')), 'int32')