tf.metrics.precision_at_k

tf.metrics.precision_at_k(
    labels,
    predictions,
    k,
    class_id=None,
    weights=None,
    metrics_collections=None,
    updates_collections=None,
    name=None
)

Defined in tensorflow/python/ops/metrics_impl.py.

Computes precision@k of the predictions with respect to sparse labels.

If class_id is specified, we calculate precision by considering only the entries in the batch for which class_id is in the top-k highest predictions, and computing the fraction of them for which class_id is indeed a correct label. If class_id is not specified, we'll calculate precision as how often on average a class among the top-k classes with the highest predicted values of a batch entry is correct and can be found in the label for that entry.

precision_at_k creates two local variables, true_positive_at_<k> and false_positive_at_<k>, that are used to compute the precision@k frequency. This frequency is ultimately returned as precision_at_<k>: an idempotent operation that simply divides true_positive_at_<k> by total (true_positive_at_<k> + false_positive_at_<k>).

For estimation of the metric over a stream of data, the function creates an update_op operation that updates these variables and returns the precision_at_<k>. Internally, a top_k operation computes a Tensor indicating the top k predictions. Set operations applied to top_k and labels calculate the true positives and false positives weighted by weights. Then update_op increments true_positive_at_<k> and false_positive_at_<k> using these values.

If weights is None, weights default to 1. Use weights of 0 to mask values.

Args:

• labels: int64 Tensor or SparseTensor with shape [D1, ... DN, num_labels] or [D1, ... DN], where the latter implies num_labels=1. N >= 1 and num_labels is the number of target classes for the associated prediction. Commonly, N=1 and labels has shape [batch_size, num_labels]. [D1, ... DN] must match predictions. Values should be in range [0, num_classes), where num_classes is the last dimension of predictions. Values outside this range are ignored.
• predictions: Float Tensor with shape [D1, ... DN, num_classes] where N >= 1. Commonly, N=1 and predictions has shape [batch size, num_classes]. The final dimension contains the logit values for each class. [D1, ... DN] must match labels.
• k: Integer, k for @k metric.
• class_id: Integer class ID for which we want binary metrics. This should be in range [0, num_classes], where num_classes is the last dimension of predictions. If class_id is outside this range, the method returns NAN.
• weights: Tensor whose rank is either 0, or n-1, where n is the rank of labels. If the latter, it must be broadcastable to labels (i.e., all dimensions must be either 1, or the same as the corresponding labels dimension).
• metrics_collections: An optional list of collections that values should be added to.
• updates_collections: An optional list of collections that updates should be added to.
• name: Name of new update operation, and namespace for other dependent ops.

Returns:

• precision: Scalar float64 Tensor with the value of true_positives divided by the sum of true_positives and false_positives.
• update_op: Operation that increments true_positives and false_positives variables appropriately, and whose value matches precision.

Raises:

• ValueError: If weights is not None and its shape doesn't match predictions, or if either metrics_collections or updates_collections are not a list or tuple.
• RuntimeError: If eager execution is enabled.