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KNeighbors with Sklearn



14 min


Model Type:


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About the Model

In this episode of ML Tips, we embark on a journey to unlock the full potential of scikit-learn's KNeighbors model. Our exploration begins with an in-depth analysis of the n_neighbors hyperparameter, unraveling the subtle nuances it introduces to our models. Once we've grasped the influence of varying neighbor counts, we venture further into the realm of clustering. Discover how to harness the power of different neighbors that yield optimal results, and witness the magic as we plot the centroids of our predictions in a mesmerizing 3D Scatter Plot using Plotly. This high-level inspection of our clusters offers a unique perspective on the inner workings of our machine learning models. Join us as we delve into the art of parameter tuning and the visualization of cluster centers in this exciting ML journey.

Free Python Code Example of KNeighbors model in Sklearn

A Little Bit more about KNeighbors

How Does k-NN Work?

Classification: In k-NN classification, when you want to predict the class of a new data point, the algorithm identifies the k-training data points that are closest (i.e., most similar) to the new point based on a distance metric (commonly Euclidean distance). The class that occurs most frequently among these k neighbors becomes the predicted class for the new data point.

Regression: In k-NN regression, the algorithm predicts the numerical value of a new data point by averaging or weighting the values of its k nearest neighbors.

Key Parameters:

n_neighbors: This is the most crucial hyperparameter in k-NN. It defines the number of neighbors to consider when making predictions. A small value (e.g., 1 or 3) makes the model sensitive to noise, while a larger value can make the model too biased.

Distance Metric: The choice of distance metric (e.g., Euclidean, Manhattan, Minkowski) affects how "closeness" is measured between data points.

Weighting: In some implementations, you can assign weights to neighbors based on their distance. Closer neighbors may have more influence on the prediction.


Simple and easy to understand.

Can be effective for small to moderately sized datasets.

Works well when decision boundaries are not linear or when data has complex patterns.


Sensitive to the choice of k and the distance metric.

Inefficient for large datasets since it requires calculating distances for every data point.

Can perform poorly when features are not on the same scale.

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Real World Applications of kNeighbors

  1. Anomaly Detection:

    • k-NN can be used to detect anomalies or outliers in datasets. Data points that are significantly different from their k-nearest neighbors may be flagged as anomalies. This is useful in fraud detection, network security, and quality control.

  2. Medical Diagnosis:

    • In healthcare, k-NN can be employed for disease diagnosis by comparing patient data to historical cases with known outcomes.

    • It can also be used for personalized medicine to recommend treatments based on patient similarities.

  3. Geographic Information Systems (GIS):

    • k-NN is used in GIS for tasks like finding the nearest gas station, restaurant, or other points of interest.

    • It can also be applied to spatial interpolation, predicting values at unmeasured locations based on neighboring measurements.

  4. Text Classification:

    • In natural language processing (NLP), k-NN can classify text documents into categories by comparing their word or document vectors to those of labeled examples.

    • It can also be used for spam email detection.

  5. Customer Segmentation:

    • Businesses can use k-NN to segment customers into groups with similar buying behavior or demographics. This helps in targeted marketing and product recommendations.

  6. Quality Control:

    • k-NN can be applied in manufacturing for quality control by comparing measurements of products to those of known good or defective items.

  7. Environmental Monitoring:

    • In environmental science, k-NN can be used for tasks such as pollution source identification, species habitat modeling, and climate data analysis.

  8. Predictive Maintenance:

    • In industries like manufacturing and aviation, k-NN can predict when machines or equipment are likely to fail based on the similarity of their operational data to historical failures.

  9. Financial Forecasting:

    • k-NN can be used for stock price prediction and portfolio optimization by analyzing historical price trends and market data.

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