About the Design Editor
The Design Editor provides prebuilt standard designs to allow a user with a minimal knowledge of the subject to quickly create experiments. You can apply engineering knowledge to define variable ranges and apply constraints to exclude impractical points. You can increase modeling sophistication by altering optimality criteria, forcing or removing specific design points, and optimally augmenting existing designs with additional points.
There is a step-by-step guide to using the Design Editor in Design of Experiments.
Opening the Design Editor
You must first have a test plan before you can open the Design Editor.
From the startup (project) view of the Model Browser, click New and select a one or two-stage test plan.
You can design experiments at both stages, for local models and global models; for most two-stage models the global model is most appropriate for design of experiment.
Before you design an experiment we recommend that you set up your input variables, by double-clicking the Inputs blocks on the test plan diagram. See Edit Model Inputs.
You can choose the number of inputs for your model and set up their names and definitions, then you can design an experiment to collect data. It is much easier to understand your design points if they are labeled with the factor names. Also, if you do not set up model inputs first, then you can only create designs for the default number of variables (one).
If you want to use optimal designs, then the type of model you are going to use to fit the data is important, and you should choose a model type before opening the Design Editor. Double-click a model block in the test plan diagram to set up model types. Optimal designs are best for cases with high system knowledge, where previous studies have given confidence on the best type of model to be fitted, so in these cases you should pick your model type before designing an experiment.
If you have no idea what model you are going to fit, choose a space-filling design. Model type has no effect on designs that are space-filling or classical, so if you want to create these designs you can leave the model type at the default and open the Design Editor.
You can invoke the Design Editor in several ways from the Edit Test Plan Definition:
First you must select the stage (first/local or second/global) for which you want to design an experiment. Click to select the appropriate model block in the test plan diagram.
Right-click the model block and select Design Experiment.
Alternatively, click the Design Experiment toolbar icon
.You can also select TestPlan > Design Experiment.
For an existing design, View > Design Data also launches the Design Editor (also in the right-click menu on each Model block). This shows the selected data as a design.
Design Styles
The Design Editor provides the interface for building experimental designs. You can make three different styles of design: classical, space-filling, and optimal.
Classical designs (including full factorial) are very well researched and are suitable for simple regions (hypercube or sphere). See Create a Classical Design.
Space-filling designs are better when there is low system knowledge. In cases where you are not sure what type of model is appropriate, and the constraints are uncertain, space-filling designs collect data in such as a way as to maximize coverage of the factors' ranges as quickly as possible. See Create a Space-Filling Design.
Optimal designs are best for cases with high system knowledge, where previous studies have given confidence in the best type of model to be fitted, and the constraints of the system are well understood. See Create an Optimal Design.
You can augment any design by optimally adding points. Working in this way allows new experiments to enhance the original, rather than simply being a second attempt to gain the necessary knowledge. See Adding and Editing Design Points.
Viewing Designs
When you first create or open a design, the main display area shows the default Design Table view of the design (see example above). All the views on the right show the design selected in the left tree (see The Design Tree). There is a context menu for the views on the right, available by right-clicking the title bars, in which you can change the view of the design to 1-D, 2-D, 3-D, 4-D, and Pairwise Projections, 2-D, and 3-D Constraint views, and the Table view (also under View menu). This menu also allows you to split the display either horizontally or vertically so that you simultaneously have two different views on the current design. The split can also be merged again. You can also use the toolbar buttons. After splitting, each view has the same functionality; that is, you can continue to split views until you have as many as you want. When you click a view, its title bar becomes blue to show it is the current active view. See Design Display Options for more information about how to change your display options.
The information pane, bottom left, displays pieces of information for the current design selected in the tree. The amount of information in this pane can change depending on what the design is capable of; for example, only certain models can support the optimal designs and only these can show current optimal values. You can also see this information and more by selecting File > Properties or using the context menu in the tree.
The Design Editor can display multiple design views at once, so while working on a design you can keep a table of design points open in one corner of the window, a 3D projection of the constraints below it, and a 2D, 3D, or pairwise plot of the current design points as the main plot.
The Design Tree
The currently available designs are displayed on the left in a tree structure.
The tree displays three pieces of information:
The name of the design, which you can edit by clicking it
The state of the design
The icon changes from
if it is empty, to
the appropriate icon for the design type when it
has design points (for
example,
optimized, as in
the toolbar buttons for Optimal, Classical, and
Space-Filling designs). The icon changes to
when design points
have been added using a different method (for
example, augmenting a classical design with
optimally chosen points). It becomes a
custom design style. You can
mix and match all design options in this
way.A padlock appears (
) if the design is
locked. This happens when it has child nodes (to
maintain the relationship between designs, so you
can retreat back up the design tree to reverse
changes).
The design that is selected as best. This is the default design that is used for matching against experimental data. The icon for the selected design is the normal icon turned blue. When you have created more than one design, you should select as best the design to be used in modeling, using the Edit menu. Blue icons are also locked designs, and do not acquire padlocks when they have child nodes.
You can reach a context menu by right-clicking in the design tree pane. Here you can delete or rename designs and add new designs. Choose Evaluate Design to open the Design Evaluation window. Properties opens the Design Properties dialog box, which displays information about the size, constraints, properties (such as optimality values), and modification dates of the selected design.
Design Display Options
In the View menu:
Current View — Changes the current view to your selection from the sub menu:
Design Table
1D Design Projection
2D Design Projection
3D Design Projection
4D Design Projection
Pairwise Design Projections
2D Constraints
3D Constraints
Model Description
View Options — these items depend on the currently selected view:
Plot Properties— For 1D, 2D and 3D Design Projections. Opens dialog boxes for configuring details of the current display. You can change basic properties such as color on the projections (1D, 2D, 3D, and 4D). You can rotate all 3D views as usual.
Edit Colormap For the 3D and 4D Design Projections. You can also double-click the color bar to edit the colormap.
Graph Size For the Pairwise Projections, you can choose graph size or to display all graphs.
Value Filter — For the table view, you can set up a filter to selectively display certain ranges of values.
Display Design Point Numbers — You can select this option to toggle the display of design point numbers in views that support the feature. A design point number is the index of a particular point in the design: this value is permanently displayed in the table view. Views that support the display of design point numbers are
2D Design Projection
3D Design Projection
4D Design Projection
Pairwise Design Projections
Because all these views are projections that use a subset of the design's input factors, it is often the case that the resulting view contains points that have been plotted on top of each other. In this case, the design point numbers will stack up in a column above the common point to aid readability. You can use Display Design Point Count to see at a glance how many points are overlapping in any stack. You can select point count or point numbers but not both.
Note
Displaying multiple views with design point numbers for large designs can significantly slow down the display. You might want to turn off the design point number display in these cases.
Display Design Point Count — If points are plotted on top of each other (in 2D, 3D, 4D, or pairwise plots) this option allows you to see how many points are overlapping in each cluster. A number next to a point indicates that more than one point is plotted there.
Print to Figure — This option copies the current view into its own figure, allowing you to use the standard MATLAB® plotting tools to annotate and print the display.
In the Tools menu:
Prediction Error Variance Viewer — Opens the Prediction Error Variance Viewer where you can evaluate the predictive power of your designs. See Prediction Error Variance Viewer.
Evaluate Designs — Opens the Design Evaluation window where you can examine detailed mathematical properties of your design. Also in the context menu in the design tree. See Design Evaluation Tool.
