Heat Maps

Heat Maps are used to depict continuous values that are typically obtained using a density estimation method that estimates a continuous density model from discrete data.

Appropriate use and design of color scales is crucial for heat maps. (The rainbow color map should be avoided because it tries to represent a quantity (continuous value) through different hues, which has the unintended impact of categorization. The human eye only uses intensity to comprehend a continuous value). Perceptually uniform color scales should be used. Color Brewer is a good source for such scales. Matplotlib also has decent color scales.