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# Copyright 2017 The TensorFlow Authors. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
# ==============================================================================
"""Functions for computing metrics like precision, recall, CorLoc and etc."""
from __future__ import division
import numpy as np
def compute_precision_recall(scores, labels, num_gt):
"""Compute precision and recall.
Args:
scores: A float numpy array representing detection score
labels: A boolean numpy array representing true/false positive labels
num_gt: Number of ground truth instances
Raises:
ValueError: if the input is not of the correct format
Returns:
precision: Fraction of positive instances over detected ones. This value is
None if no ground truth labels are present.
recall: Fraction of detected positive instance over all positive instances.
This value is None if no ground truth labels are present.
"""
if (
not isinstance(labels, np.ndarray)
or labels.dtype != np.bool
or len(labels.shape) != 1
):
raise ValueError("labels must be single dimension bool numpy array")
if not isinstance(scores, np.ndarray) or len(scores.shape) != 1:
raise ValueError("scores must be single dimension numpy array")
if num_gt < np.sum(labels):
raise ValueError(
"Number of true positives must be smaller than num_gt."
)
if len(scores) != len(labels):
raise ValueError("scores and labels must be of the same size.")
if num_gt == 0:
return None, None
sorted_indices = np.argsort(scores)
sorted_indices = sorted_indices[::-1]
labels = labels.astype(int)
true_positive_labels = labels[sorted_indices]
false_positive_labels = 1 - true_positive_labels
cum_true_positives = np.cumsum(true_positive_labels)
cum_false_positives = np.cumsum(false_positive_labels)
precision = cum_true_positives.astype(float) / (
cum_true_positives + cum_false_positives
)
recall = cum_true_positives.astype(float) / num_gt
return precision, recall
def compute_average_precision(precision, recall):
"""Compute Average Precision according to the definition in VOCdevkit.
Precision is modified to ensure that it does not decrease as recall
decrease.
Args:
precision: A float [N, 1] numpy array of precisions
recall: A float [N, 1] numpy array of recalls
Raises:
ValueError: if the input is not of the correct format
Returns:
average_precison: The area under the precision recall curve. NaN if
precision and recall are None.
"""
if precision is None:
if recall is not None:
raise ValueError("If precision is None, recall must also be None")
return np.NAN
if not isinstance(precision, np.ndarray) or not isinstance(
recall, np.ndarray
):
raise ValueError("precision and recall must be numpy array")
if precision.dtype != np.float or recall.dtype != np.float:
raise ValueError("input must be float numpy array.")
if len(precision) != len(recall):
raise ValueError("precision and recall must be of the same size.")
if not precision.size:
return 0.0
if np.amin(precision) < 0 or np.amax(precision) > 1:
raise ValueError("Precision must be in the range of [0, 1].")
if np.amin(recall) < 0 or np.amax(recall) > 1:
raise ValueError("recall must be in the range of [0, 1].")
if not all(recall[i] <= recall[i + 1] for i in range(len(recall) - 1)):
raise ValueError("recall must be a non-decreasing array")
recall = np.concatenate([[0], recall, [1]])
precision = np.concatenate([[0], precision, [0]])
# Preprocess precision to be a non-decreasing array
for i in range(len(precision) - 2, -1, -1):
precision[i] = np.maximum(precision[i], precision[i + 1])
indices = np.where(recall[1:] != recall[:-1])[0] + 1
average_precision = np.sum(
(recall[indices] - recall[indices - 1]) * precision[indices]
)
return average_precision
def compute_cor_loc(
num_gt_imgs_per_class, num_images_correctly_detected_per_class
):
"""Compute CorLoc according to the definition in the following paper.
https://www.robots.ox.ac.uk/~vgg/rg/papers/deselaers-eccv10.pdf
Returns nans if there are no ground truth images for a class.
Args:
num_gt_imgs_per_class: 1D array, representing number of images containing
at least one object instance of a particular class
num_images_correctly_detected_per_class: 1D array, representing number of
images that are correctly detected at least one object instance of a
particular class
Returns:
corloc_per_class: A float numpy array represents the corloc score of each
class
"""
# Divide by zero expected for classes with no gt examples.
with np.errstate(divide="ignore", invalid="ignore"):
return np.where(
num_gt_imgs_per_class == 0,
np.nan,
num_images_correctly_detected_per_class / num_gt_imgs_per_class,
)
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