This example shows a line graph of stock closing prices over time, with the line colored by a red-to-black-to-green gradient that maps to the y-axis value. The graph uses D3.js (version 3.5.17) with SVG rendering, and applies the gradient via a `linearGradient` definition referenced by the line’s `stroke` attribute. Data is loaded from a CSV file using `d3.csv`, and axes are generated with `d3.svg.axis`. The gradient stops are explicitly defined in code to create color bands at 40% and 62% of the vertical range.