Trivariate Data

The chapter introduces different approaches for the visualization of trivariate data. Observations in this case are represented by triplets of values (x, y, z) where the third variable z is typically numeric and continuous, whereas x and y can be either numerical (discrete or continuous) or categorical. The solution is to plot the data on the xy plane and delegate the encoding of z to marker size and/or color. In this context there are two scenarios: (a) x and y are continuous variables and (b) x and y are numerical discrete or categorical variables. The chapter describes solutions for both situations, respectively scatter bubble plots for (a) and heat maps and lattice bubble plots for (b).