D3 multi-series line chart with tooltips and legend
This interactive multi-series line chart displays four data columns over time, with a dropdown menu to switch between three value groups. Users hover over the lines to see tooltips with the series name, formatted value, and date, powered by the jQuery Tipsy plugin. The visualization uses D3.js v3 to render SVG elements, including axes and animated transitions when the selection changes, while a legend updates based on the current data subset. Data is loaded from a CSV file using `d3.csv`.