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Visualizations with Display Objects#

In this example, we will construct display objects, ConfusionMatrixDisplay, RocCurveDisplay, and PrecisionRecallDisplay directly from their respective metrics. This is an alternative to using their corresponding plot functions when a model’s predictions are already computed or expensive to compute. Note that this is advanced usage, and in general we recommend using their respective plot functions.

# Authors: The scikit-learn developers
# SPDX-License-Identifier: BSD-3-Clause

Load Data and train model#

For this example, we load a blood transfusion service center data set from OpenML. This is a binary classification problem where the target is whether an individual donated blood. Then the data is split into a train and test dataset and a logistic regression is fitted with the train dataset.

fromsklearn.datasetsimport fetch_openml
fromsklearn.linear_modelimport LogisticRegression
fromsklearn.model_selectionimport train_test_split
fromsklearn.pipelineimport make_pipeline
fromsklearn.preprocessingimport StandardScaler
X, y = fetch_openml (data_id=1464, return_X_y=True)
X_train, X_test, y_train, y_test = train_test_split (X, y, stratify=y)
clf = make_pipeline (StandardScaler (), LogisticRegression (random_state=0))
clf.fit(X_train, y_train)

Pipeline(steps=[('standardscaler', StandardScaler()),
 ('logisticregression', LogisticRegression(random_state=0))])
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Create ConfusionMatrixDisplay #

With the fitted model, we compute the predictions of the model on the test dataset. These predictions are used to compute the confusion matrix which is plotted with the ConfusionMatrixDisplay 

fromsklearn.metricsimport ConfusionMatrixDisplay , confusion_matrix
y_pred = clf.predict(X_test)
cm = confusion_matrix (y_test, y_pred)
cm_display = ConfusionMatrixDisplay (cm).plot()
plot display object visualization

Create RocCurveDisplay #

The roc curve requires either the probabilities or the non-thresholded decision values from the estimator. Since the logistic regression provides a decision function, we will use it to plot the roc curve:

fromsklearn.metricsimport RocCurveDisplay , roc_curve
y_score = clf.decision_function(X_test)
fpr, tpr, _ = roc_curve (y_test, y_score, pos_label=clf.classes_[1])
roc_display = RocCurveDisplay (fpr=fpr, tpr=tpr).plot()
plot display object visualization

Create PrecisionRecallDisplay #

Similarly, the precision recall curve can be plotted using y_score from the prevision sections.

fromsklearn.metricsimport PrecisionRecallDisplay , precision_recall_curve
prec, recall, _ = precision_recall_curve (y_test, y_score, pos_label=clf.classes_[1])
pr_display = PrecisionRecallDisplay (precision=prec, recall=recall).plot()
plot display object visualization

Combining the display objects into a single plot#

The display objects store the computed values that were passed as arguments. This allows for the visualizations to be easliy combined using matplotlib’s API. In the following example, we place the displays next to each other in a row.

importmatplotlib.pyplotasplt
fig, (ax1, ax2) = plt.subplots (1, 2, figsize=(12, 8))
roc_display.plot(ax=ax1)
pr_display.plot(ax=ax2)
plt.show ()
plot display object visualization

Total running time of the script: (0 minutes 0.313 seconds)

Related examples

Precision-Recall

Precision-Recall

ROC Curve with Visualization API

ROC Curve with Visualization API

Multiclass Receiver Operating Characteristic (ROC)

Multiclass Receiver Operating Characteristic (ROC)

Post-tuning the decision threshold for cost-sensitive learning

Post-tuning the decision threshold for cost-sensitive learning

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