Visualizing heat maps

The heat map is a graph where the individual values contained in a matrix are represented through gradations of colors. Both fractal maps and tree maps often use the same color-coding systems to represent the hierarchy of a variable. For example, if we measure the number of clicks on a web page or the areas where the mouse pointer passes the most often, we will obtain a heat map with certain areas highlighted by warm colors, that is, those that most attract our attention.

Getting ready

We'll look at how to visualize heat maps in this recipe. This is a pictorial representation of data, where two groups are associated point by point. The individual values that are contained in a matrix are represented...