sklearn.metrics
.precision_score¶
- sklearn.metrics.precision_score(y_true, y_pred, *, labels=None, pos_label=1, average='binary', sample_weight=None, zero_division='warn')[source]¶
Compute the precision.
The precision is the ratio
tp / (tp + fp)
wheretp
is the number of true positives andfp
the number of false positives. The precision is intuitively the ability of the classifier not to label as positive a sample that is negative.The best value is 1 and the worst value is 0.
Support beyond term:
binary
targets is achieved by treating multiclass and multilabel data as a collection of binary problems, one for each label. For the binary case, settingaverage='binary'
will return precision forpos_label
. Ifaverage
is not'binary'
,pos_label
is ignored and precision for both classes are computed, then averaged or both returned (whenaverage=None
). Similarly, for multiclass and multilabel targets, precision for alllabels
are either returned or averaged depending on theaverage
parameter. Uselabels
specify the set of labels to calculate precision for.Read more in the User Guide.
- Parameters:
- y_true1d array-like, or label indicator array / sparse matrix
Ground truth (correct) target values.
- y_pred1d array-like, or label indicator array / sparse matrix
Estimated targets as returned by a classifier.
- labelsarray-like, default=None
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 in multiclass classification to exclude a “negative class”. Labels not present in the data can be included and will be “assigned” 0 samples. For multilabel targets, labels are column indices. By default, all labels iny_true
andy_pred
are used in sorted order.Changed in version 0.17: Parameter
labels
improved for multiclass problem.- pos_labelint, float, bool or str, default=1
The class to report if
average='binary'
and the data is binary, otherwise this parameter is ignored. For multiclass or multilabel targets, setlabels=[pos_label]
andaverage != 'binary'
to report metrics for one label only.- average{‘micro’, ‘macro’, ‘samples’, ‘weighted’, ‘binary’} or None, default=’binary’
This parameter is required for multiclass/multilabel targets. 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 F-score 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_weightarray-like of shape (n_samples,), default=None
Sample weights.
- zero_division{“warn”, 0.0, 1.0, np.nan}, default=”warn”
Sets the value to return when there is a zero division.
Notes: - If set to “warn”, this acts like 0, but a warning is also raised. - If set to
np.nan
, such values will be excluded from the average.New in version 1.3:
np.nan
option was added.
- Returns:
- precisionfloat (if average is not None) or array of float of shape (n_unique_labels,)
Precision of the positive class in binary classification or weighted average of the precision of each class for the multiclass task.
See also
precision_recall_fscore_support
Compute precision, recall, F-measure and support for each class.
recall_score
Compute the ratio
tp / (tp + fn)
wheretp
is the number of true positives andfn
the number of false negatives.PrecisionRecallDisplay.from_estimator
Plot precision-recall curve given an estimator and some data.
PrecisionRecallDisplay.from_predictions
Plot precision-recall curve given binary class predictions.
multilabel_confusion_matrix
Compute a confusion matrix for each class or sample.
Notes
When
true positive + false positive == 0
, precision returns 0 and raisesUndefinedMetricWarning
. This behavior can be modified withzero_division
.Examples
>>> import numpy as np >>> from sklearn.metrics import precision_score >>> y_true = [0, 1, 2, 0, 1, 2] >>> y_pred = [0, 2, 1, 0, 0, 1] >>> precision_score(y_true, y_pred, average='macro') 0.22... >>> precision_score(y_true, y_pred, average='micro') 0.33... >>> precision_score(y_true, y_pred, average='weighted') 0.22... >>> precision_score(y_true, y_pred, average=None) array([0.66..., 0. , 0. ]) >>> y_pred = [0, 0, 0, 0, 0, 0] >>> precision_score(y_true, y_pred, average=None) array([0.33..., 0. , 0. ]) >>> precision_score(y_true, y_pred, average=None, zero_division=1) array([0.33..., 1. , 1. ]) >>> precision_score(y_true, y_pred, average=None, zero_division=np.nan) array([0.33..., nan, nan])
>>> # multilabel classification >>> y_true = [[0, 0, 0], [1, 1, 1], [0, 1, 1]] >>> y_pred = [[0, 0, 0], [1, 1, 1], [1, 1, 0]] >>> precision_score(y_true, y_pred, average=None) array([0.5, 1. , 1. ])
Examples using sklearn.metrics.precision_score
¶
Probability Calibration curves