Histographs: Interactive Visualization of Complex Data with Graphs

Graphs are a widely used and understood visualization. However, they quickly break down when the visualized data is quite complex, requiring hundreds or thousands of graphs. Our Histographs system builds on the techniques introduced with Information Murals [7] to enable meaningful visualization of such data. Histographs map the frequency of data elements at each display location to luminance, revealing data density and trends. Our improvements include contrast-weighted histogram equalization to improve the frequency-luminance mapping, splatting to make outliers visible, a second derivative modulation to reveal changes in data trends, and the use of line integral convolution show local data flow. Different data-to-space mappings can be implemented interactively. A linked correlation matrix display and highlights inter-graph relationships. Users can zoom in on data, as well as select with shapeand correlation-based brushing. Histographs are a useful way of obtaining data overviews, and revealing hidden structure in complex data sets.