Purpose: The source file has divided the urban area of Hangzhou into 1000m x 1000m grids, each containing various features such as road network density, population density, etc. The grids have been filtered to include only those within the influence range of subway stations (800m, 10-minute walking distance). To find the nearest subway station for each grid, this code was written. This will help in observing the characteristics around each subway station in subsequent analyses.