NUMBAT OER - Open Educational Resources

4.3 More than two variables

Obviously, it is only possible to represent the relationship between two variables in twodimensional space. It is possible to group scatter plots into a matrix to represent all possible pairs of bivariate relationships within a set of observations of several variables. Alternatively, there are multivariate analyses that represent the overall variability in a dataset with many variables as a series of new summary variables, and the results can then be displayed in two dimensions.

In the case of three variables, an isometric three-dimensional plot can be used. Data points are often shown attached to the 'floor' of the plot (so-called 'ball on stick' plots) to provide a better spatial reference for the two dimensional representation of threedimensional space. The three-dimensional equivalent of a regression line is a surface.