This example visualizes the progression of a line chart tracking a signal over time using D3.js. It reads CSV data files containing time-series measurements and displays them as multiple filtered lines on an SVG canvas. The code uses D3 v3’s `d3.svg.line`, `d3.time.scale`, and `d3.svg.axis` to render the chart with a date-based x-axis and linear y-axis. Interactive mouse-over effects are partially implemented, though the mouse-line overlay is not fully functional.