This example shows the classic Iris dataset in a parallel coordinate plot, with four axes for sepal and petal measurements. A dropdown selector toggles the y-axis scale between a fixed global range ("union") and per-axis independent ranges ("self"), which visually emphasizes feature clustering differences. The code uses D3 v5 with `d3.scaleLinear` and `d3.extent` to compute scales, `d3.axisLeft` for tick marks, and `d3.drag` to reposition axes interactively. Semi-transparent polylines are colored by species, and axes can be reordered by dragging, with smooth transitions via D3's `.transition()` API.