def test_auc(x, y, expected):
# Test Area Under Curve (AUC) computation
assert auc(torch.tensor(x), torch.tensor(y), reorder=True) == expected
def _auroc_compute(
preds: torch.Tensor,
target: torch.Tensor,
mode: str,
num_classes: Optional[int] = None,
pos_label: Optional[int] = None,
average: Optional[str] = 'macro',
max_fpr: Optional[float] = None,
sample_weights: Optional[Sequence] = None,
) -> torch.Tensor:
# binary mode override num_classes
if mode == 'binary':
num_classes = 1
# check max_fpr parameter
if max_fpr is not None:
if (not isinstance(max_fpr, float) and 0 < max_fpr <= 1):
raise ValueError(
f"`max_fpr` should be a float in range (0, 1], got: {max_fpr}")
if LooseVersion(torch.__version__) < LooseVersion('1.6.0'):
raise RuntimeError(
"`max_fpr` argument requires `torch.bucketize` which"
" is not available below PyTorch version 1.6")
# max_fpr parameter is only support for binary
if mode != 'binary':
raise ValueError(
f"Partial AUC computation not available in"
f" multilabel/multiclass setting, 'max_fpr' must be"
f" set to `None`, received `{max_fpr}`.")
# calculate fpr, tpr
if mode == 'multi-label':
# for multilabel we iteratively evaluate roc in a binary fashion
output = [
roc(preds[:, i],
target[:, i],
num_classes=1,
pos_label=1,
sample_weights=sample_weights) for i in range(num_classes)
]
fpr = [o[0] for o in output]
tpr = [o[1] for o in output]
else:
fpr, tpr, _ = roc(preds, target, num_classes, pos_label,
sample_weights)
# calculate standard roc auc score
if max_fpr is None or max_fpr == 1:
if num_classes != 1:
# calculate auc scores per class
auc_scores = [auc(x, y) for x, y in zip(fpr, tpr)]
# calculate average
if average == AverageMethods.NONE:
return auc_scores
elif average == AverageMethods.MACRO:
return torch.mean(torch.stack(auc_scores))
elif average == AverageMethods.WEIGHTED:
if mode == DataType.MULTILABEL:
support = torch.sum(target, dim=0)
else:
support = torch.bincount(target.flatten(),
minlength=num_classes)
return torch.sum(
torch.stack(auc_scores) * support / support.sum())
allowed_average = [e.value for e in AverageMethods]
raise ValueError(
f"Argument `average` expected to be one of the following:"
f" {allowed_average} but got {average}")
return auc(fpr, tpr)
max_fpr = torch.tensor(max_fpr, device=fpr.device)
# Add a single point at max_fpr and interpolate its tpr value
stop = torch.bucketize(max_fpr, fpr, out_int32=True, right=True)
weight = (max_fpr - fpr[stop - 1]) / (fpr[stop] - fpr[stop - 1])
interp_tpr = torch.lerp(tpr[stop - 1], tpr[stop], weight)
tpr = torch.cat([tpr[:stop], interp_tpr.view(1)])
fpr = torch.cat([fpr[:stop], max_fpr.view(1)])
# Compute partial AUC
partial_auc = auc(fpr, tpr)
# McClish correction: standardize result to be 0.5 if non-discriminant
# and 1 if maximal
min_area = 0.5 * max_fpr**2
max_area = max_fpr
return 0.5 * (1 + (partial_auc - min_area) / (max_area - min_area))