A ternary plot can be used to examine relations between four dimensions where three of those dimensions represent components of a mixture (i.e., the relations between them is constrained such that the values of the three variables add up to the same constant). One typical application of this graph is when the measured response(s) from an experiment depends on the relative proportions of three components (e.g., three different chemicals) that are varied in order to determine an optimal combination of those components (e.g., in mixture designs).

For plotting three (X, Y, and Z) or four (X, Y, Z, and V) variables, ternary plot display options include triangular shaped 2D Scatterplots or Contour plots with contours defined by either lines or areas. Triangular (prism) shaped plots are available for plotting four variables (Surface Plots) or for more than four variables (i.e., X, Y, Z, and V1�Vn) using 3D Scatterplots or Trace Plots. Linear and Quadratic as well as Full Cubic and Special Cubic fits can be applied to all ternary plots except the 2D Scatterplot and Trace ternary plot types (See Ternary Fit Types for more details).

See also, Graphs - Ternary Graphs and the Conceptual Overview for Ternary Plots.