imblearn.metrics
.geometric_mean_score¶

imblearn.metrics.
geometric_mean_score
(y_true, y_pred, labels=None, pos_label=1, average='multiclass', sample_weight=None, correction=0.0)[source]¶ Compute the geometric mean.
The geometric mean (Gmean) is the root of the product of classwise sensitivity. This measure tries to maximize the accuracy on each of the classes while keeping these accuracies balanced. For binary classification Gmean is the squared root of the product of the sensitivity and specificity. For multiclass problems it is a higher root of the product of sensitivity for each class.
For compatibility with other imbalance performance measures, Gmean can be calculated for each class separately on a onevsrest basis when
average != 'multiclass'
.The best value is 1 and the worst value is 0. Traditionally if at least one class is unrecognized by the classifier, Gmean resolves to zero. To alleviate this property, for highly multiclass the sensitivity of unrecognized classes can be “corrected” to be a user specified value (instead of zero). This option works only if
average == 'multiclass'
.Read more in the User Guide.
 Parameters
 y_truendarray, shape (n_samples, )
Ground truth (correct) target values.
 y_predndarray, shape (n_samples, )
Estimated targets as returned by a classifier.
 labelslist, optional
The set of labels to include when
average != 'binary'
, and their order ifaverage is None
. Labels present in the data can be excluded, for example to calculate a multiclass average ignoring a majority negative class, while labels not present in the data will result in 0 components in a macro average. pos_labelstr or int, optional (default=1)
The class to report if
average='binary'
and the data is binary. If the data are multiclass, this will be ignored; settinglabels=[pos_label]
andaverage != 'binary'
will report scores for that label only. averagestr or None, optional (default=’multiclass’)
If
None
, the scores for each class are returned. Otherwise, this determines the type of averaging performed on the data:'binary'
:Only report results for the class specified by
pos_label
. This is applicable only if targets (y_{true,pred}
) are binary.'micro'
:Calculate metrics globally by counting the total true positives, false negatives and false positives.
'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). This alters ‘macro’ to account for label imbalance; it can result in an Fscore that is not between precision and recall.
'samples'
:Calculate metrics for each instance, and find their average (only meaningful for multilabel classification where this differs from
accuracy_score
).
 sample_weightndarray, shape (n_samples, )
Sample weights.
 correction: float, optional (default=0.0)
Substitutes sensitivity of unrecognized classes from zero to a given value.
 Returns
 geometric_meanfloat
Notes
See Metrics specific to imbalanced learning.
References
 1
Kubat, M. and Matwin, S. “Addressing the curse of imbalanced training sets: onesided selection” ICML (1997)
 2
Barandela, R., Sánchez, J. S., Garcıa, V., & Rangel, E. “Strategies for learning in class imbalance problems”, Pattern Recognition, 36(3), (2003), pp 849851.
Examples
>>> from imblearn.metrics import geometric_mean_score >>> y_true = [0, 1, 2, 0, 1, 2] >>> y_pred = [0, 2, 1, 0, 0, 1] >>> geometric_mean_score(y_true, y_pred) 0.0 >>> geometric_mean_score(y_true, y_pred, correction=0.001) 0.010000000000000004 >>> geometric_mean_score(y_true, y_pred, average='macro') 0.47140452079103168 >>> geometric_mean_score(y_true, y_pred, average='micro') 0.47140452079103168 >>> geometric_mean_score(y_true, y_pred, average='weighted') 0.47140452079103168 >>> geometric_mean_score(y_true, y_pred, average=None) array([ 0.8660254, 0. , 0. ])