Line Chart with Multiple Lines
This line chart displays one week of temperature data for cities worldwide, sourced from Data Canvas - Sense Your City. Each line represents a city, with temperature on the y-axis and time on the x-axis. The code uses d3’s `scaleTime`, `scaleLinear`, `scaleOrdinal`, `axisBottom`, `axisLeft`, `line`, and `curveBasis` to create smooth, colored paths with `nest().key()` for grouping. A custom `colorLegend` function renders the categorical color scale, while `mix-blend-mode: multiply` gives overlapping lines a blended appearance.