Data - Surface Plot
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You must fit a response surface design model with two or more continuous variables before you can generate a surface plot. Surface plot does not use the data in the worksheet. Instead, Minitab looks in the worksheet for a stored model to obtain the necessary information.

Minitab automatically stores the most recent model that you fit for each response variable. To view information about models that are stored in the worksheet, click View Model in the Surface Plot dialog.