Specify the settings for Surface Plot

Surface Plot > Settings

This dialog box varies by the type of model that you used to fit the data.

In This Topic

All model types except factorial designs, screening designs, and mixture designs
Factorial designs and screening designs
Mixture designs

All model types except factorial designs, screening designs, and mixture designs

A surface plot can include only two continuous variables. If a model has more than two continuous variables, Minitab holds each factor that is not on the contour plot constant. If a model has categorical variables, Minitab also holds the categorical variables constant.

Hold continuous variables at

Variable: Shows all the continuous variables in your model but not on the plot. This column does not take any input.
Setting: By default, for the continuous variables that are not in the plot, the setting for each variable is its mean. If you want to use a different value, delete the mean value and enter a new value.

Hold categorical variables at

Variable: Shows all the categorical variables in your model. This column does not take any input.
Setting: All categorical variables in the model must be held at a constant value. Select a level at which to hold the variables. The default value is either the lowest numeric value or the first alphabetical value.

Factorial designs and screening designs

A surface plot can include only two continuous factors. If a model has more than two continuous factors, Minitab holds each factor that is not on the contour plot constant. If a model has categorical factors or covariates, Minitab holds these values constant.

Hold factors at

Variable: Shows all the categorical factors and continuous factors that you controlled in your experimental design but are not on the plot. This column does not take any input.
Setting: All categorical factors in the model must be held at a constant value. Select a level at which to hold the variables. By default, for the continuous factors that are not in the plot, the setting for each variable is its mean. If you want to use a different value, delete the mean value and enter a new value.

Hold covariates at

Variable: Shows all the covariates in your model. Covariates are the continuous variables that you did not control in your experimental design. This column does not take any input.
Setting: All covariates in a factorial design must be held at a constant value. By default, the setting for each covariate is its mean. If you want to use a different value, delete the mean value and enter a new value.

Mixture designs

You can set the holding level for components and process variables that are not in the plot at their highest or lowest settings, or you can set specific levels to hold each. The hold values must be expressed in the units as follows:

Components must be in the units as displayed in the worksheet.
Process variables must be in coded units.

For more information, go to What is the difference between coded units and uncoded units?.

Note

If your mixture design contains text process variables, you can only set their holding values at one of the text levels.

Hold components at

Lower bound setting: Select to set all components that are not on the plot at their lower bound.
Middle setting: Select to set all components that are not on the plot at their middle setting.
Upper bound setting: Select to set all components that are not on the plot at their highest bound.
Component: Shows all the components in your design. This column does not take any input.
Name: Shows all the names of the components in your design. This column does not take any input.
Setting: Enter a value to hold each component that is not on the plot.

Hold process variables at

Low setting: Select to set process variables that are not on the plot at their lowest setting.
Middle setting: Select to set all process variables that are not on the plot at their middle setting.
High setting: Select to set process variables that are not on the plot at their highest setting.
Process Var.: Shows all the process variables in your design. This column does not take any input.
Name: Shows all the names of the process variables in your design. This column does not take any input.
Setting: Enter a value to hold each process variable that is not on the plot.

Hold mixture amount at: Select a total at which to hold the mixture amount.