What is k-median

K-median is a popular clustering algorithm in machine learning that is commonly used for partitioning a set of data points into k clusters. This algorithm is different from other partitioning methods because it is based on the median of a set of points rather than their mean.

In essence, the k-median algorithm aims to minimize the total distance between each point in a cluster and its respective median. The median, or central point, is calculated as the point that has the smallest sum of distances to all other points within the cluster.

To better understand how this works, let’s consider a simple example. Suppose we have a dataset of 20 points and we want to partition them into three clusters using the k-median algorithm. We first randomly choose three points as the initial medians for each cluster. Then, we assign each of the remaining points to the nearest median based on the Euclidean distance between the point and the median.

Next, we will calculate the median for each cluster based on the assigned points. This new median will become the center point for that cluster. We will then repeat this process until the medians no longer change. This means that the algorithm has converged and the clusters are well-defined.

One important advantage of using k-median over other clustering methods is that it is highly resistant to outliers, or data points that lie far away from the rest of the data. Because the algorithm uses the median as the center point for each cluster, it is not influenced by outliers that might skew the mean or average of the dataset.

Another benefit of using k-median is that it is relatively fast and efficient. Compared to other clustering algorithms such as k-means, which require multiple iterations and can take a long time to converge, k-median typically requires fewer iterations and thus can perform clustering more quickly.

In summary, k-median is a powerful algorithm for partitioning data into k clusters based on their median. It is resistant to outliers and performs well in high-dimensional datasets. Moreover, it can be used in a variety of different applications, such as image recognition, natural language processing, and recommendation systems. As machine learning continues to advance, k-median will likely remain an important tool for clustering and data analysis.