Source code for monai.metrics.rocauc

# Copyright 2020 - 2021 MONAI Consortium
# 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.

import warnings
from typing import Callable, List, Optional, Union, cast

import numpy as np
import torch

from monai.networks import one_hot
from monai.utils import Average


def _calculate(y: torch.Tensor, y_pred: torch.Tensor) -> float:
    if not (y.ndimension() == y_pred.ndimension() == 1 and len(y) == len(y_pred)):
        raise AssertionError("y and y_pred must be 1 dimension data with same length.")
    if not y.unique().equal(torch.tensor([0, 1], dtype=y.dtype, device=y.device)):
        raise AssertionError("y values must be 0 or 1, can not be all 0 or all 1.")
    n = len(y)
    indices = y_pred.argsort()
    y = y[indices].cpu().numpy()
    y_pred = y_pred[indices].cpu().numpy()
    nneg = auc = tmp_pos = tmp_neg = 0.0

    for i in range(n):
        y_i = cast(float, y[i])
        if i + 1 < n and y_pred[i] == y_pred[i + 1]:
            tmp_pos += y_i
            tmp_neg += 1 - y_i
            continue
        if tmp_pos + tmp_neg > 0:
            tmp_pos += y_i
            tmp_neg += 1 - y_i
            nneg += tmp_neg
            auc += tmp_pos * (nneg - tmp_neg / 2)
            tmp_pos = tmp_neg = 0
            continue
        if y_i == 1:
            auc += nneg
        else:
            nneg += 1
    return auc / (nneg * (n - nneg))


[docs]def compute_roc_auc( y_pred: torch.Tensor, y: torch.Tensor, to_onehot_y: bool = False, softmax: bool = False, other_act: Optional[Callable] = None, average: Union[Average, str] = Average.MACRO, ) -> Union[np.ndarray, List[float], float]: """Computes Area Under the Receiver Operating Characteristic Curve (ROC AUC). Referring to: `sklearn.metrics.roc_auc_score <https://scikit-learn.org/stable/modules/generated/ sklearn.metrics.roc_auc_score.html#sklearn.metrics.roc_auc_score>`_. Args: y_pred: input data to compute, typical classification model output. it must be One-Hot format and first dim is batch, example shape: [16] or [16, 2]. y: ground truth to compute ROC AUC metric, the first dim is batch. example shape: [16, 1] will be converted into [16, 2] (where `2` is inferred from `y_pred`). to_onehot_y: whether to convert `y` into the one-hot format. Defaults to False. softmax: whether to add softmax function to `y_pred` before computation. Defaults to False. other_act: callable function to replace `softmax` as activation layer if needed, Defaults to ``None``. for example: `other_act = lambda x: torch.log_softmax(x)`. average: {``"macro"``, ``"weighted"``, ``"micro"``, ``"none"``} Type of averaging performed if not binary classification. Defaults to ``"macro"``. - ``"macro"``: calculate metrics for each label, and find their unweighted mean. This does not take label imbalance into account. - ``"weighted"``: calculate metrics for each label, and find their average, weighted by support (the number of true instances for each label). - ``"micro"``: calculate metrics globally by considering each element of the label indicator matrix as a label. - ``"none"``: the scores for each class are returned. Raises: ValueError: When ``y_pred`` dimension is not one of [1, 2]. ValueError: When ``y`` dimension is not one of [1, 2]. ValueError: When ``softmax=True`` and ``other_act is not None``. Incompatible values. TypeError: When ``other_act`` is not an ``Optional[Callable]``. ValueError: When ``average`` is not one of ["macro", "weighted", "micro", "none"]. Note: ROCAUC expects y to be comprised of 0's and 1's. `y_pred` must be either prob. estimates or confidence values. """ y_pred_ndim = y_pred.ndimension() y_ndim = y.ndimension() if y_pred_ndim not in (1, 2): raise ValueError("Predictions should be of shape (batch_size, n_classes) or (batch_size, ).") if y_ndim not in (1, 2): raise ValueError("Targets should be of shape (batch_size, n_classes) or (batch_size, ).") if y_pred_ndim == 2 and y_pred.shape[1] == 1: y_pred = y_pred.squeeze(dim=-1) y_pred_ndim = 1 if y_ndim == 2 and y.shape[1] == 1: y = y.squeeze(dim=-1) if y_pred_ndim == 1: if to_onehot_y: warnings.warn("y_pred has only one channel, to_onehot_y=True ignored.") if softmax: warnings.warn("y_pred has only one channel, softmax=True ignored.") return _calculate(y, y_pred) n_classes = y_pred.shape[1] if to_onehot_y: y = one_hot(y, n_classes) if softmax and other_act is not None: raise ValueError("Incompatible values: softmax=True and other_act is not None.") if softmax: y_pred = y_pred.float().softmax(dim=1) if other_act is not None: if not callable(other_act): raise TypeError(f"other_act must be None or callable but is {type(other_act).__name__}.") y_pred = other_act(y_pred) if y.shape != y_pred.shape: raise AssertionError("data shapes of y_pred and y do not match.") average = Average(average) if average == Average.MICRO: return _calculate(y.flatten(), y_pred.flatten()) y, y_pred = y.transpose(0, 1), y_pred.transpose(0, 1) auc_values = [_calculate(y_, y_pred_) for y_, y_pred_ in zip(y, y_pred)] if average == Average.NONE: return auc_values if average == Average.MACRO: return np.mean(auc_values) if average == Average.WEIGHTED: weights = [sum(y_) for y_ in y] return np.average(auc_values, weights=weights) raise ValueError(f'Unsupported average: {average}, available options are ["macro", "weighted", "micro", "none"].')