Density Plot

Overview

A density plot is similar to a scatter plot, but instead of plotting each point, an invisible grid is overlayed on the graph, and all points within the same grid bin are represented by a single marker whose size is proportional to the number of points in that bin. This technique is useful for large data sets when data density is important, or when a scatter plot over-complicates the representation. Markers may optionally be colored according to the average value of some measure of the points in the corresponding bin.

This type of graph was originally described in "Scatterplot Matrix Techniques for Large N" by Carr et al. Journal of the American Statistical Association No.82, 1987, pp. 424-436

The cells of the density plot can be sized according to:

• The number of data points within each cell
• The average value of some variable, taken over all data points within that cell
• Or cells may be drawn at a uniform size

The cells can be colored according to:

• The number of data points within each cell
• The average value of some variable, taken over all data points within that cell
• The most common row color, taken over all data points within that cell
• Or all cells may be drawn in the same color