Scatterplots are used for showing the joint values of two quantitative variables. Here we use a subset of the data of the National Health and Nutrition Examination Survey (NHANES) that are available in the package NHANES. You must select appropriate variables to be represented (only numerical) and a grouping variable (categorical). Lines can be added to show the trend on the data. Prediction intervals are an option.
3D scatterplots are used for representing values of three continous variables. You can add information on other variables through the color and size of points. Here we use color for each gender. You can point at each point to retrieve its information.