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Computes the Intersection-Over-Union metric for one-hot encoded labels.
tf.keras.metrics.OneHotIoU(
num_classes,
target_class_ids,
name=None,
dtype=None,
ignore_class=None,
sparse_y_pred=False,
axis=-1
)
Formula:
iou = true_positives / (true_positives + false_positives + false_negatives)
Intersection-Over-Union is a common evaluation metric for semantic image segmentation.
To compute IoUs, the predictions are accumulated in a confusion matrix,
weighted by sample_weight
and the metric is then calculated from it.
If sample_weight
is None
, weights default to 1.
Use sample_weight
of 0 to mask values.
This class can be used to compute IoU for multi-class classification tasks
where the labels are one-hot encoded (the last axis should have one
dimension per class). Note that the predictions should also have the same
shape. To compute the IoU, first the labels and predictions are converted
back into integer format by taking the argmax over the class axis. Then the
same computation steps as for the base IoU
class apply.
Note, if there is only one channel in the labels and predictions, this class
is the same as class IoU
. In this case, use IoU
instead.
Also, make sure that num_classes
is equal to the number of classes in the
data, to avoid a "labels out of bound" error when the confusion matrix is
computed.
Example:
Example:
y_true = np.array([[0, 0, 1], [1, 0, 0], [0, 1, 0], [1, 0, 0]])
y_pred = np.array([[0.2, 0.3, 0.5], [0.1, 0.2, 0.7], [0.5, 0.3, 0.1],
[0.1, 0.4, 0.5]])
sample_weight = [0.1, 0.2, 0.3, 0.4]
m = keras.metrics.OneHotIoU(num_classes=3, target_class_ids=[0, 2])
m.update_state(
y_true=y_true, y_pred=y_pred, sample_weight=sample_weight)
# cm = [[0, 0, 0.2+0.4],
# [0.3, 0, 0],
# [0, 0, 0.1]]
# sum_row = [0.3, 0, 0.7], sum_col = [0.6, 0.3, 0.1]
# true_positives = [0, 0, 0.1]
# single_iou = true_positives / (sum_row + sum_col - true_positives))
# mean_iou = (0 / (0.3 + 0.6 - 0) + 0.1 / (0.7 + 0.1 - 0.1)) / 2
m.result()
0.071
Usage with compile()
API:
model.compile(
optimizer='sgd',
loss='mse',
metrics=[keras.metrics.OneHotIoU(
num_classes=3,
target_class_id=[1]
)]
)
Attributes | |
---|---|
dtype
|
|
variables
|
Methods
add_variable
add_variable(
shape, initializer, dtype=None, aggregation='sum', name=None
)
add_weight
add_weight(
shape=(), initializer=None, dtype=None, name=None
)
from_config
@classmethod
from_config( config )
get_config
get_config()
Return the serializable config of the metric.
reset_state
reset_state()
Reset all of the metric state variables.
This function is called between epochs/steps, when a metric is evaluated during training.
result
result()
Compute the intersection-over-union via the confusion matrix.
stateless_reset_state
stateless_reset_state()
stateless_result
stateless_result(
metric_variables
)
stateless_update_state
stateless_update_state(
metric_variables, *args, **kwargs
)
update_state
update_state(
y_true, y_pred, sample_weight=None
)
Accumulates the confusion matrix statistics.
Args | |
---|---|
y_true
|
The ground truth values. |
y_pred
|
The predicted values. |
sample_weight
|
Optional weighting of each example. Can
be a Tensor whose rank is either 0, or the same as y_true ,
and must be broadcastable to y_true . Defaults to 1 .
|
Returns | |
---|---|
Update op. |
__call__
__call__(
*args, **kwargs
)
Call self as a function.