D3 allows us to build rich custom visualizations by leveraging DOM elements and data. Here, we combine a small visualization which demonstrates the use of a map together with a small bar chart.
CSS selectors are used here to allow the client to connect between map and bar chart. Thanks to the use of Topojson, a JSON based format for geo-spatial data, it is possible to create rich visualizations which can load up on the client in a short space of time, compared to traditional JSON data. Here below is a short example of the project which looks at water levels of various rivers in the south east of the U.K.