A line chart displays stock closing prices over time for two datasets. An "Update" button triggers an animated transition between the datasets, smoothly interpolating both the line path and the x- and y-axes using D3.js transitions with a 750-millisecond duration. The visualization uses d3.svg.line, d3.time.scale for time-based x-axis formatting, and d3.svg.axis, with data loaded from CSV files via d3.csv. The SVG path and axes are updated in place, demonstrating dynamic data swapping.