PIN Numbers Analyzed

A great example of visual analytics:

In this heatmap, the x-axis depicts the left two digits from [00] to [99] and the y-axis depicts the right two digits from [00] to [99]. The bottom left is 0000 and the top right is 9999.

Color is used to represent frequency. The higher frequency occurences are yellow to white hot, and the lower frequency occurences are red, through dark red to black.