dataset.models.metrics

Metrics

class Metrics(*args, **kwargs)

Base metrics evaluation class

This class is not supposed to be instantiated. Use specific children classes instead (e.g. ClassificationMetrics).

Examples

m = ClassificationMetrics(targets, predictions, num_classes=10, fmt='labels')
m.evaluate(['sensitivity', 'specificity'], multiclass='micro')

evaluate(metrics, agg='mean', *args, **kwargs)

Calculates metrics

Parameters:

• metrics (str or list of str) – metric names

• agg (str) – inter-batch aggregation type

• args – metric-specific parameters

• kwargs – metric-specific parameters

Returns:

if metrics is a list, then a dict is returned::

• key - metric name

• value - metric value

Return type:

metric value or dict

ClassificationMetrics

class ClassificationMetrics(targets, predictions, fmt='proba', num_classes=None, axis=None, threshold=0.5, skip_bg=False, calc=True)

Bases: Metrics

Metrics to assess classification models

Parameters:

• targets (np.array) – Ground-truth labels / probabilities / logits

• predictions (np.array) – Predicted labels / probabilites / logits

• num_classes (int) – the number of classes (default is None)

• fmt ('proba', 'logits', 'labels') – whether arrays contain probabilities, logits or labels

• axis (int) – a class axis (default is None)

• threshold (float) – A probability level for binarization (lower values become 0, equal or greater values become 1)

Notes

• Input arrays (targets and predictions) might be vectors or multidimensional arrays, where the first dimension represents batch items. The latter is useful for pixel-level metrics.

• Both targets and predictions usually contain the same data (labels, probabilities or logits). However, targets might be labels, while predictions are probabilities / logits. For that to work:

  • targets should have the shape which exactly 1 dimension smaller, than predictions shape;

  • axis should point to that dimension;

  • fmt should contain format of predictions.

• When axis is specified, predictions should be a one-hot array with class information provided in the given axis (class probabilities or logits). In this case targets can contain labels (see above) or probabilities / logits in the very same axis.

• If fmt is ‘labels’, num_classes should be specified. Due to randomness any given batch may not contain items of some classes, so all the labels cannot be inferred as simply as labels.max().

• If fmt is ‘proba’ or ‘logits’, then axis points to the one-hot dimension. However, if axis is None, two class classification is assumed and targets / predictions should contain probabilities or logits for a positive class only.

Metrics All metrics return:

• a single value if input is a vector for a 2-class task.

• a single value if input is a vector for a multiclass task and multiclass averaging is enabled.

• a vector with batch size items if input is a multidimensional array (e.g. images or sequences) and there are just 2 classes or multiclass averaging is on.

• a vector with num_classes items if input is a vector for multiclass case without averaging.

• a 2d array (batch_items, num_classes) for multidimensional inputs in a multiclass case without averaging.

Note

Count-based metrics (true_positive, false_positive, etc.) do not support mutliclass averaging. They always return counts for each class separately. For multiclass tasks rate metrics, such as true_positive_rate, false_positive_rate, etc., might seem more convenient.

Multiclass metrics

In a multiclass case metrics might be calculated with or without class averaging.

Available methods are:

• None - no averaging, calculate metrics for each class individually (one-vs-all)

• ‘micro’ - calculate metrics globally by counting the total true positives,

  false negatives, false positives, etc. across all classes

• ‘macro’ - calculate metrics for each class, and take their mean.

Examples

metrics = ClassificationMetrics(targets, predictions, num_classes=10, fmt='labels')
metrics.evaluate(['sensitivity', 'specificity'], multiclass='macro')

accuracy()

An accuracy of detecting all the classes combined

append(metrics)

Append confusion matrix with data from another metrics

condition_negative(label=None, *args, **kwargs)

condition_positive(label=None, *args, **kwargs)

property confusion_matrix

copy()

Return a duplicate containing only the confusion matrix

diagnostics_odds_ratio(*args, when_zero=(inf, 0), **kwargs)

f1_score(*args, **kwargs)

Compute f1-score

false_discovery_rate(*args, when_zero=(1, 0), **kwargs)

false_negative(label=None, *args, **kwargs)

false_negative_rate(*args, when_zero=(1, 0), **kwargs)

false_omission_rate(*args, when_zero=(1, 0), **kwargs)

false_positive(label=None, *args, **kwargs)

false_positive_rate(*args, when_zero=(1, 0), **kwargs)

free()

Free memory allocated for intermediate data

jaccard(*args, **kwargs)

negative_likelihood_ratio(*args, when_zero=(inf, 0), **kwargs)

negative_predictive_value(*args, when_zero=(0, 1), **kwargs)

one_hot(inputs)

Convert an array of labels into a one-hot array

plot_confusion_matrix(classes=None, normalize=False, **kwargs)

Plot confusion matrix.

Parameters:

• classes (sequence, optional) – Sequence of classes labels.

• normalize (bool) – Whether to normalize confusion matrix over target classes.

positive_likelihood_ratio(*args, when_zero=(inf, 0), **kwargs)

positive_predictive_value(*args, when_zero=(0, 1), **kwargs)

prediction_negative(label=None, *args, **kwargs)

prediction_positive(label=None, *args, **kwargs)

prevalence(*args, when_zero=(0, 0), **kwargs)

Notes

Parameter when_zero doesn’t really matter in this case, since total_population is never zero, when targets are not empty.

total_population(*args, **kwargs)

true_negative(label=None, *args, **kwargs)

true_negative_rate(*args, when_zero=(0, 1), **kwargs)

true_positive(label=None, *args, **kwargs)

true_positive_rate(*args, when_zero=(0, 1), **kwargs)

update(metrics)

Update confusion matrix with data from another metrics

SegmentationMetricsByPixels

class SegmentationMetricsByPixels(targets, predictions, fmt='proba', num_classes=None, axis=None, threshold=0.5, skip_bg=False, calc=True)

Bases: ClassificationMetrics

Metrics to assess segmentation models pixel-wise

Notes

Rate metrics are evaluated for each item independently. So there are two levels of metrics aggregation:

• multi-class averaging

• dataset aggregation.

For instance, if you have a dataset of 100 pictures (each having size of 256x256) of 10 classes and you need to calculate an accuracy of semantic segmentation, then:

• evaluate([‘accuracy’], agg=None, multiclass=None) will return an array of shape (100, 10) containing accuracy of each class for each image separately.

• evaluate([‘accuracy’], agg=’mean’, multiclass=None) will return a vector of shape (10,) containing an accuracy of each class averaged across all images.

• evaluate([‘accuracy’], agg=None, multiclass=’macro’) will return a vector of shape (100,) containing an accuracy of each image separately averaged across all classes.

• evaluate([‘accuracy’], agg=’mean’, multiclass=’macro’) will return a single value of an average accuracy of all classes and images combined.

The default values are agg=’mean’, multiclass=’macro’.

For multi-class averaging see ClassificationMetrics.

Examples

metrics = SegmentationMetricsByPixels(targets, predictions, num_classes=10, fmt='labels')
metrics.evaluate('specificity')
metrics.evaluate(['sensitivity', 'jaccard'], agg='mean', multiclass=None)

SegmentationMetricsByInstances

class SegmentationMetricsByInstances(targets, predictions, fmt='proba', num_classes=None, axis=None, skip_bg=True, threshold=0.5, iot=0.5, calc=True)

Bases: ClassificationMetrics

Metrics to assess segmentation models by instances (i.e. connected components of one class, e.g. cancer nodules, faces, )

Parameters:

iot (float) – if the ratio of a predicted instance size to the corresponding target size >= iot, then instance is considered correctly predicted (true postitive).

Notes

For other parameters see ClassificationMetrics.

condition_positive(label=None, *args, **kwargs)

free()

Free memory allocated for intermediate data

prediction_positive(label=None, *args, **kwargs)

total_population(label=None, *args, **kwargs)

true_negative(label=None, *args, **kwargs)

true_positive(label=None, *args, **kwargs)