Elbow Plot

Definition: The elbow plot is a graphical tool used to determine the optimal number of clusters in K-means clustering.

Procedure:

1. Run the K-means clustering algorithm for a range of (k) values (number of clusters).
2. Calculate the Within-Cluster Sum of Squares (WCSS) for each (k).

WCSS: WCSS is the sum of squared distances between each point and the centroid of its assigned cluster. It measures the compactness of the clusters.

Plot:

• X-axis: Number of clusters (k).
• Y-axis: WCSS.

Interpretation:

• As (k) increases, WCSS decreases, indicating more compact clusters.
• The plot typically shows a point where the reduction in WCSS slows down, forming an "elbow" shape.

Optimal (k): The optimal number of clusters is often at the "elbow" point, where adding another cluster does not significantly reduce WCSS.

Usage: The elbow plot helps to balance between underfitting (too few clusters) and overfitting (too many clusters), providing a heuristic method for choosing the right number of clusters.