Line Chart with Multiple Lines
This line chart displays one week of temperature data in degrees Celsius for cities worldwide, sourced from Data Canvas - Sense Your City. It uses d3.csv to load the dataset, with d3.scaleTime and d3.scaleLinear for the axes, and d3.nest to group readings by city. Multiple lines are rendered using d3.line with a curveBasis interpolation, while d3.scaleOrdinal assigns categorical colors. A custom colorLegend function generates the city legend, and d3.axisBottom and d3.axisLeft create gridlines.