Florence Nightingale

A British statistician who believed a picture, drawn honestly, could show what lists of numbers alone could not. In 1858 she invented the polar-area diagram (a fan of coloured wedges, each wedge's area proportional to the count it stood for) to make complex monthly data instantly readable. Her diagram is one of the earliest examples of a custom visualisation designed to make a clear case from data; she used it to argue, successfully, for changes that had previously been resisted because the underlying figures were too tedious for decision-makers to follow. She later became the first woman elected to the Royal Statistical Society.