Adjusting mesh resolution
main topics 

Contour plots, 3D surface plots, and 3D wireframe plots are based on a grid of evenly spaced x- and y-values called a mesh. By default, if your data form a regular x-y mesh, Minitab plots the actual z-values at the x-y mesh intersections. If your data are irregular, Minitab interpolates z-values for the intersections of a regular 15 by 15 mesh. The mesh automatically extends across the range of x- and y-values.

The number of x- and y-values on a mesh determines its resolution. You can change the mesh resolution. A higher resolution mesh (one with more x- and y-values) will result in a finer interpolation of the surface or contours. The following wireframe and contour plots show the same data but use different mesh resolutions. (Gridlines on the contour plots show approximate mesh location.)

 When x-y data do not form a regular grid, the mesh resolution could have a large effect on the contour or surface plot. If your data were sampled such that your x-y points are close to a regular grid,  you might enhance the fit by specifying a mesh similar to that of your data.

For example, you want to investigate the effect of temperature and pressure on cook time. You have 4 temperature settings (325, 350, 375, 400) and 3 pressure settings (5, 10, 15). When you run the experiment, however, the  temperature was slightly different than the desired setting for several runs; thus, the data won't quite form a regular grid. However, because your temperature values are close to regular, a 4 x 3 mesh (temperature x pressure) might give good results for your contour and surface plots.