You can fit one of several equations to the data or use one of the data smoothing procedures in a 3D surface plot by selecting one of the predefined functions described below:

Linear. Select Linear to fit a linear surface (e.g., Z = a + bX + cY) to the points in the 3D scatterplot.

Quadratic. Select Quadratic to fit a second-order polynomial surface to the points in the 3D scatterplot.

Least squares. Select Least squares to fit a surface to the XYZ coordinate data according to the distance-weighted least squares smoothing procedure (the influence of individual points decreases with the horizontal distance from the respective points on the surface); the stiffness of the fit can be controlled in the Fitting dialog. For more information, see Distance-Weighted Least Squares.

Negative exponential. Select Negative exponential to fit a surface to the XYZ coordinate data according to the negative exponentially weighted smoothing procedure (the influence of individual points decreases exponentially with the horizontal distance from the respective points on the surface); the stiffness of the fit can be controlled on the Plot: Fitting tab of the Graph Options dialog box. For more information, see Negative Exponentially Weighted Fitting.

Spline. Select Spline to fit a surface to the XYZ coordinate data using the bicubic spline smoothing procedure. For more information, see Spline Fitting.