What is K-means Clustering?

by Stephen M. Walker II, Co-Founder / CEO

What is K-means Clustering?

K-means clustering is an unsupervised machine learning algorithm that aims to partition a dataset into k distinct clusters based on their similarity or dissimilarity with respect to certain features or attributes. The goal of k-means clustering is to minimize the total within-cluster variance, which can be achieved by iteratively updating the cluster centroids and reassigning samples to their closest centroid until convergence.

K-means clustering involves the following steps:

  1. Initialization — Randomly select k initial centroids from the input dataset, where each centroid represents the mean or center of a cluster.
  2. Assignment — For each sample in the dataset, compute its Euclidean distance to all k centroids and assign it to the closest centroid, forming k distinct clusters with their associated samples.
  3. Update — Recalculate the new centroids for each cluster by taking the mean of all samples assigned to that cluster, effectively moving them closer to the center of mass of the data points within the cluster.
  4. Convergence check — Repeat steps 2 and 3 until the centroids no longer change significantly or a maximum number of iterations is reached. At this point, the algorithm has converged to a local optimum solution where each sample is assigned to its closest centroid, forming k distinct clusters with minimal within-cluster variance.

Some key advantages of k-means clustering include:

  1. Efficiency — K-means clustering has linear time complexity in the size of the input dataset, making it suitable for handling large-scale or high-dimensional data.
  2. Intuitive interpretation — The resulting clusters can be easily visualized and analyzed using various tools such as scatter plots, histograms, or parallel coordinate plots, providing valuable insights into the underlying structure or patterns within the input data.
  3. Scalability — K-means clustering can be applied to different kinds of input data (e.g., continuous, discrete) and is relatively insensitive to outliers or irrelevant variables within the dataset.
  4. Interactivity — Users can interactively explore the clusters by adjusting the value of k or modifying other hyperparameters such as the distance measure or initialization strategy, allowing for more flexible and customizable clustering solutions.

However, k-means clustering may not perform well on datasets with complex or non-convex cluster structures, as it assumes that each cluster can be accurately represented by a single centroid and relies heavily on the Euclidean distance measure to assess similarity between samples. Additionally, the algorithm is sensitive to initial parameter settings such as the choice of centroids or initialization strategy, which can affect its overall performance and convergence rate on specific datasets.

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