This scatterplot visualizes the relationship between patient age and medical insurance charges across over 1,000 records from a Kaggle dataset. Each green circle represents an individual, with age plotted on the x-axis and charges on the y-axis, revealing a general upward trend in costs with age. The React app loads data from a CSV file using d3.csv, then the viz.js module applies d3.scaleLinear and d3.extent to map values to screen coordinates, rendering circles with d3’s selection and join methods.