This example visualizes fraud email attack frequency as a day/hour heatmap, with hours along the y-axis and days of the week across the x-axis. The code uses D3 v3’s `d3.json` to fetch data from a Solr index and from a GitHub-hosted GDP dataset, though only the latter is parsed with `d3.timeParse`. It renders a bordered rectangle grid via SVG, with monospaced axis labels styled through CSS classes. The dataset picker element is present but not implemented, and the GDP data is only logged to the console, not yet mapped to the heatmap cells.