KNN Neighborhood Explorer

Watch k, distance metric and feature scaling reshape a k-nearest-neighbour decision boundary.

k-NN
decision boundary
scaling
bias-variance

Query prediction

Patient #0 is truly benign. Averaging the 9 nearest neighbors in 20 dimensions gives a predicted probability of 0.111 (cohort prevalence: 0.217).

Neighborhood in 2D PCA projection

Distance from query to every other case

Prediction for this patient as k grows

Curse of dimensionality: distance concentration

Nearest neighborFarthest neighbor

When 'nearest' stops meaning anything

As dimensions increase, the nearest and farthest curves converge: the ratio of nearest to farthest distance approaches 1, and every point becomes roughly equidistant from every other point. Reduce "Dimensions used" back toward 2 and watch the neighborhood snap back into a meaningful local structure.

Preparing the simulation…