# Source code for pytorch_lightning.metrics.functional.stat_scores

```
# Copyright The PyTorch Lightning team.
#
# 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.
from typing import Optional, Tuple
import torch
from pytorch_lightning.metrics.classification.helpers import _input_format_classification
def _del_column(tensor: torch.Tensor, index: int):
""" Delete the column at index."""
return torch.cat([tensor[:, :index], tensor[:, (index + 1):]], 1)
def _stat_scores(
preds: torch.Tensor,
target: torch.Tensor,
reduce: str = "micro",
) -> Tuple[torch.Tensor, torch.Tensor, torch.Tensor, torch.Tensor]:
"""Calculate the number of tp, fp, tn, fn.
Args:
preds:
An ``(N, C)`` or ``(N, C, X)`` tensor of predictions (0 or 1)
target:
An ``(N, C)`` or ``(N, C, X)`` tensor of true labels (0 or 1)
reduce:
One of ``'micro'``, ``'macro'``, ``'samples'``
Return:
Returns a list of 4 tensors; tp, fp, tn, fn.
The shape of the returned tensors depnds on the shape of the inputs
and the ``reduce`` parameter:
If inputs are of the shape ``(N, C)``, then
- If ``reduce='micro'``, the returned tensors are 1 element tensors
- If ``reduce='macro'``, the returned tensors are ``(C,)`` tensors
- If ``reduce'samples'``, the returned tensors are ``(N,)`` tensors
If inputs are of the shape ``(N, C, X)``, then
- If ``reduce='micro'``, the returned tensors are ``(N,)`` tensors
- If ``reduce='macro'``, the returned tensors are ``(N,C)`` tensors
- If ``reduce='samples'``, the returned tensors are ``(N,X)`` tensors
"""
if reduce == "micro":
dim = [0, 1] if preds.ndim == 2 else [1, 2]
elif reduce == "macro":
dim = 0 if preds.ndim == 2 else 2
elif reduce == "samples":
dim = 1
true_pred, false_pred = target == preds, target != preds
pos_pred, neg_pred = preds == 1, preds == 0
tp = (true_pred * pos_pred).sum(dim=dim)
fp = (false_pred * pos_pred).sum(dim=dim)
tn = (true_pred * neg_pred).sum(dim=dim)
fn = (false_pred * neg_pred).sum(dim=dim)
return tp.long(), fp.long(), tn.long(), fn.long()
def _stat_scores_update(
preds: torch.Tensor,
target: torch.Tensor,
reduce: str = "micro",
mdmc_reduce: Optional[str] = None,
num_classes: Optional[int] = None,
top_k: Optional[int] = None,
threshold: float = 0.5,
is_multiclass: Optional[bool] = None,
ignore_index: Optional[int] = None,
) -> Tuple[torch.Tensor, torch.Tensor, torch.Tensor, torch.Tensor]:
preds, target, _ = _input_format_classification(
preds, target, threshold=threshold, num_classes=num_classes, is_multiclass=is_multiclass, top_k=top_k
)
if ignore_index is not None and not 0 <= ignore_index < preds.shape[1]:
raise ValueError(f"The `ignore_index` {ignore_index} is not valid for inputs with {preds.shape[0]} classes")
if ignore_index is not None and preds.shape[1] == 1:
raise ValueError("You can not use `ignore_index` with binary data.")
if preds.ndim == 3:
if not mdmc_reduce:
raise ValueError(
"When your inputs are multi-dimensional multi-class, you have to set the `mdmc_reduce` parameter"
)
if mdmc_reduce == "global":
preds = torch.transpose(preds, 1, 2).reshape(-1, preds.shape[1])
target = torch.transpose(target, 1, 2).reshape(-1, target.shape[1])
# Delete what is in ignore_index, if applicable (and classes don't matter):
if ignore_index is not None and reduce != "macro":
preds = _del_column(preds, ignore_index)
target = _del_column(target, ignore_index)
tp, fp, tn, fn = _stat_scores(preds, target, reduce=reduce)
# Take care of ignore_index
if ignore_index is not None and reduce == "macro":
tp[..., ignore_index] = -1
fp[..., ignore_index] = -1
tn[..., ignore_index] = -1
fn[..., ignore_index] = -1
return tp, fp, tn, fn
def _stat_scores_compute(tp: torch.Tensor, fp: torch.Tensor, tn: torch.Tensor, fn: torch.Tensor) -> torch.Tensor:
outputs = [
tp.unsqueeze(-1),
fp.unsqueeze(-1),
tn.unsqueeze(-1),
fn.unsqueeze(-1),
tp.unsqueeze(-1) + fn.unsqueeze(-1), # support
]
outputs = torch.cat(outputs, -1)
outputs = torch.where(outputs < 0, torch.tensor(-1, device=outputs.device), outputs)
return outputs
[docs]def stat_scores(
preds: torch.Tensor,
target: torch.Tensor,
reduce: str = "micro",
mdmc_reduce: Optional[str] = None,
num_classes: Optional[int] = None,
top_k: Optional[int] = None,
threshold: float = 0.5,
is_multiclass: Optional[bool] = None,
ignore_index: Optional[int] = None,
) -> torch.Tensor:
"""Computes the number of true positives, false positives, true negatives, false negatives.
Related to `Type I and Type II errors <https://en.wikipedia.org/wiki/Type_I_and_type_II_errors>`__
and the `confusion matrix <https://en.wikipedia.org/wiki/Confusion_matrix#Table_of_confusion>`__.
The reduction method (how the statistics are aggregated) is controlled by the
``reduce`` parameter, and additionally by the ``mdmc_reduce`` parameter in the
multi-dimensional multi-class case. Accepts all inputs listed in :ref:`extensions/metrics:input types`.
Args:
preds: Predictions from model (probabilities or labels)
target: Ground truth values
threshold:
Threshold probability value for transforming probability predictions to binary
(0 or 1) predictions, in the case of binary or multi-label inputs.
top_k:
Number of highest probability entries for each sample to convert to 1s - relevant
only for inputs with probability predictions. If this parameter is set for multi-label
inputs, it will take precedence over ``threshold``. For (multi-dim) multi-class inputs,
this parameter defaults to 1.
Should be left unset (``None``) for inputs with label predictions.
reduce:
Defines the reduction that is applied. Should be one of the following:
- ``'micro'`` [default]: Counts the statistics by summing over all [sample, class]
combinations (globally). Each statistic is represented by a single integer.
- ``'macro'``: Counts the statistics for each class separately (over all samples).
Each statistic is represented by a ``(C,)`` tensor. Requires ``num_classes``
to be set.
- ``'samples'``: Counts the statistics for each sample separately (over all classes).
Each statistic is represented by a ``(N, )`` 1d tensor.
Note that what is considered a sample in the multi-dimensional multi-class case
depends on the value of ``mdmc_reduce``.
num_classes:
Number of classes. Necessary for (multi-dimensional) multi-class or multi-label data.
ignore_index:
Specify a class (label) to ignore. If given, this class index does not contribute
to the returned score, regardless of reduction method. If an index is ignored, and
``reduce='macro'``, the class statistics for the ignored class will all be returned
as ``-1``.
mdmc_reduce:
Defines how the multi-dimensional multi-class inputs are handeled. Should be
one of the following:
- ``None`` [default]: Should be left unchanged if your data is not multi-dimensional
multi-class (see :ref:`extensions/metrics:input types` for the definition of input types).
- ``'samplewise'``: In this case, the statistics are computed separately for each
sample on the ``N`` axis, and then the outputs are concatenated together. In each
sample the extra axes ``...`` are flattened to become the sub-sample axis, and
statistics for each sample are computed by treating the sub-sample axis as the
``N`` axis for that sample.
- ``'global'``: In this case the ``N`` and ``...`` dimensions of the inputs are
flattened into a new ``N_X`` sample axis, i.e. the inputs are treated as if they
were ``(N_X, C)``. From here on the ``reduce`` parameter applies as usual.
is_multiclass:
Used only in certain special cases, where you want to treat inputs as a different type
than what they appear to be. See the parameter's
:ref:`documentation section <extensions/metrics:using the is_multiclass parameter>`
for a more detailed explanation and examples.
Return:
The metric returns a tensor of shape ``(..., 5)``, where the last dimension corresponds
to ``[tp, fp, tn, fn, sup]`` (``sup`` stands for support and equals ``tp + fn``). The
shape depends on the ``reduce`` and ``mdmc_reduce`` (in case of multi-dimensional
multi-class data) parameters:
- If the data is not multi-dimensional multi-class, then
- If ``reduce='micro'``, the shape will be ``(5, )``
- If ``reduce='macro'``, the shape will be ``(C, 5)``,
where ``C`` stands for the number of classes
- If ``reduce='samples'``, the shape will be ``(N, 5)``, where ``N`` stands for
the number of samples
- If the data is multi-dimensional multi-class and ``mdmc_reduce='global'``, then
- If ``reduce='micro'``, the shape will be ``(5, )``
- If ``reduce='macro'``, the shape will be ``(C, 5)``
- If ``reduce='samples'``, the shape will be ``(N*X, 5)``, where ``X`` stands for
the product of sizes of all "extra" dimensions of the data (i.e. all dimensions
except for ``C`` and ``N``)
- If the data is multi-dimensional multi-class and ``mdmc_reduce='samplewise'``, then
- If ``reduce='micro'``, the shape will be ``(N, 5)``
- If ``reduce='macro'``, the shape will be ``(N, C, 5)``
- If ``reduce='samples'``, the shape will be ``(N, X, 5)``
Example:
>>> from pytorch_lightning.metrics.functional import stat_scores
>>> preds = torch.tensor([1, 0, 2, 1])
>>> target = torch.tensor([1, 1, 2, 0])
>>> stat_scores(preds, target, reduce='macro', num_classes=3)
tensor([[0, 1, 2, 1, 1],
[1, 1, 1, 1, 2],
[1, 0, 3, 0, 1]])
>>> stat_scores(preds, target, reduce='micro')
tensor([2, 2, 6, 2, 4])
"""
if reduce not in ["micro", "macro", "samples"]:
raise ValueError(f"The `reduce` {reduce} is not valid.")
if mdmc_reduce not in [None, "samplewise", "global"]:
raise ValueError(f"The `mdmc_reduce` {mdmc_reduce} is not valid.")
if reduce == "macro" and (not num_classes or num_classes < 1):
raise ValueError("When you set `reduce` as 'macro', you have to provide the number of classes.")
if num_classes and ignore_index is not None and (not 0 <= ignore_index < num_classes or num_classes == 1):
raise ValueError(f"The `ignore_index` {ignore_index} is not valid for inputs with {num_classes} classes")
tp, fp, tn, fn = _stat_scores_update(
preds,
target,
reduce=reduce,
mdmc_reduce=mdmc_reduce,
top_k=top_k,
threshold=threshold,
num_classes=num_classes,
is_multiclass=is_multiclass,
ignore_index=ignore_index,
)
return _stat_scores_compute(tp, fp, tn, fn)
```