Pajek
Pajek is a software package for analyzing and visualizing large networks, originally developed for social network analysis but now widely used in various fields like biology, physics, and computer science. It provides tools for network decomposition, clustering, and layout algorithms to handle complex relational data efficiently.
Developers should learn Pajek when working with large-scale network data, such as social networks, citation networks, or biological interactions, where traditional tools like Excel or basic graph libraries are insufficient. It is particularly useful for researchers and data scientists who need to perform advanced network analysis, community detection, or generate publication-quality visualizations without extensive programming.