Decision Boundary Plot
Chart overview
A decision boundary plot meshes the 2D feature space and colors each point according to the class predicted by a trained classifier, revealing the geometry of the model's decision logic.
Key points
- Researchers use it to compare the complexity and flexibility of different algorithms such as SVM, k-NN, and neural networks on the same dataset.
- It is particularly informative for teaching classification concepts and for detecting overfitting through irregular boundaries.
Example Visualization

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"Create a decision boundary plot from my 2D feature data and classifier. Draw filled contour regions for each class using transparent colors, overlay the training points colored by true label, mark misclassified points with a distinct marker, and add a legend."
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Python Code Example
Console Output
Figure saved: plotivy-decision-boundary-plot.png
Common Use Cases
- 1Comparing linear vs. nonlinear classifiers on a two-feature dataset
- 2Illustrating how kernel choice affects SVM separation geometry
- 3Detecting overfitting by showing jagged boundaries on high-variance models
- 4Visualizing PCA-reduced embeddings of a multi-class dataset with class regions
Pro Tips
Use at least 200x200 mesh resolution for smooth boundary contours
Apply PCA or t-SNE first and plot in the 2D reduced space for high-dimensional data
Use low alpha (0.3 to 0.4) for the filled regions so training points remain visible
Plot both training and test points with different markers to reveal generalization
Scientific Chart Selection Cheat Sheet
Not sure whether to use a Violin Plot, Box Plot, or Ridge Plot? Download our single-page reference mapping the most-used scientific chart types, exactly when to use them, and the core Matplotlib/Seaborn functions.