sklearn.metrics
.hamming_loss¶

sklearn.metrics.
hamming_loss
(y_true, y_pred, labels=None, sample_weight=None)[source]¶ Compute the average Hamming loss.
The Hamming loss is the fraction of labels that are incorrectly predicted.
Read more in the User Guide.
 Parameters
 y_true1d arraylike, or label indicator array / sparse matrix
Ground truth (correct) labels.
 y_pred1d arraylike, or label indicator array / sparse matrix
Predicted labels, as returned by a classifier.
 labelsarray, shape = [n_labels], optional (default=’deprecated’)
Integer array of labels. If not provided, labels will be inferred from y_true and y_pred.
New in version 0.18.
Deprecated since version 0.21: This parameter
labels
is deprecated in version 0.21 and will be removed in version 0.23. Hamming loss usesy_true.shape[1]
for the number of labels when y_true is binary label indicators, so it is unnecessary for the user to specify. sample_weightarraylike of shape (n_samples,), default=None
Sample weights.
New in version 0.18.
 Returns
 lossfloat or int,
Return the average Hamming loss between element of
y_true
andy_pred
.
See also
Notes
In multiclass classification, the Hamming loss corresponds to the Hamming distance between
y_true
andy_pred
which is equivalent to the subsetzero_one_loss
function, whennormalize
parameter is set to True.In multilabel classification, the Hamming loss is different from the subset zeroone loss. The zeroone loss considers the entire set of labels for a given sample incorrect if it does not entirely match the true set of labels. Hamming loss is more forgiving in that it penalizes only the individual labels.
The Hamming loss is upperbounded by the subset zeroone loss, when
normalize
parameter is set to True. It is always between 0 and 1, lower being better.References
 1
Grigorios Tsoumakas, Ioannis Katakis. MultiLabel Classification: An Overview. International Journal of Data Warehousing & Mining, 3(3), 113, JulySeptember 2007.
 2
Examples
>>> from sklearn.metrics import hamming_loss >>> y_pred = [1, 2, 3, 4] >>> y_true = [2, 2, 3, 4] >>> hamming_loss(y_true, y_pred) 0.25
In the multilabel case with binary label indicators:
>>> import numpy as np >>> hamming_loss(np.array([[0, 1], [1, 1]]), np.zeros((2, 2))) 0.75