So far, we've looked at some fairly basic applications of color in maps, coloring single features or adding a simple ramp to choropleth data. But sometimes we want to go beyond the basic and make a map that's slightly more sophisticated in the way color represents the data, sets a mood, or works with patterns.
Moving beyond the basics
Value-by-alpha
Value-by-alpha is a technique developed by cartographers Robert Roth, Andy Woodruff, and Zach Johnson, to enable the inclusion of a second variable relating to size. Traditionally, this has been done with cartograms. This technique involves distorting the size of an area, such as states or counties, to represent their share of some variable, such as population. The value...
