Trace Plot

Trace plots are similar to perturbation plots for non-mixture designs. They are used compare the effects of all the components in the design space.

The factors tool is used to set the reference blend through which the traces are plotted. The goal is to determine how sensitive the response is to deviation from the formulation near the reference blend. The reference blend is best determined by the results of numerical optimization, but defaults to the centroid values.

The trace plots can be created using either Piepel’s or Cox’s direction.

For Piepel direction, anywhere along the trace the ratios of the changeable amounts of all the other components are held constant.

For Cox direction, anywhere along a trace the ratios of the other components are held constant to each other.

The x-axis of the plot is in pseudo (coded) units and shows the position relative to the coded scale (0 to 1 for mixtures.

If U_pseudo coding is used (see warning on trace plot) be aware that moving to the right on the X-axis on the graph is moving down in actual units.

References