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Introduction to K-Nearest Neighbors

Explore how to apply the K-Nearest Neighbors algorithm for classification tasks using Python. Understand how KNN predicts outcomes based on the closest data points and learn steps to implement, evaluate, and optimize the model for practical use.

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Quick overview

Our next supervised learning classification technique is K-Nearest Neighbors (k-NN), which classifies new unknown data points based on their proximity to known data points. This classification process is determined by setting the k number of data points closest to the target data point. For example, if you set k to 3, k-NN analyzes the nearest three data points (neighbors) to the target data point.

Example

Given the following dataset and predict the class for p (p1=3p_1=3 and p2=7p_2=7) and value of k=2k=2.

Sr. P1 P2 Class
i 7 7 B
ii 7 4 B
iii 3 4 A
iv 1 4 A
  • Euclidean distance

d(p,q)=i=1n(qipi)2d\left( p,q\right) = \sqrt {\sum _{i=1}^{n} \left( q_{i}-p_{i}\right)^2 } ...