Scatter plots are among the most basic and useful of graphical representation techniques. A scatter plot of two sets of variables is simply a two-dimensional representation of the points in a plane to show the relationship between two variables. The scatter plot is most useful in identifying the type of relationship (linear or nonlinear) between two sets of variables. Further, if the relationship is linear they help determine the negative or positive relationship between the two variables. This section uses various SAS procedures to plot scatter plots in two and three dimensions. When there are more than two variables, scatter plots of two variables at a time are displayed in a matrix of plots.