Data=>InterpolationΒΆ

To plot imported 3D datasets an interpolation must take place. Interpolation generates a grid composed of equidistant points.

../../_images/DataInterpolation-en.png

This dialog box allows you to set the range and style of interpolation and the number of points to be calculated.

Interpolation at Grid lines
When the Interpolation at Grid lines box is checked, the points will be calculated so that the grid lines of the 3D Surface Plot correspond to the tick marks of the x- and y-axes. This improves the clarity of the plot.
Range

When the Interpolation at Grid lines box is switched on, the range of the interpolation will be set automatically to the Min and Max of the x- and y-axes (see Diagram=>X/Y/Z-Axis=>Parameters). Interpolation range and density cannot be edited in this case.

Do not select this box if you want to restrict interpolation range. Instead, set interpolation range within the coordinate system.

If the points of the interpolated grid fall outside of the data hull, they will be computed by extrapolation. To plot the contour map outside of the data hull, select the non-linear interpolation method from the Type group.

Density

This function enables you to set interpolation density. The number of rows and columns belonging to the interpolation grid must lie between 5 and 100.

When you switch on Interpolation at Grid lines, the density of the grid will be automatically set and cannot be edited. These automatic settings are determined through the Min, Max, Delta and Tick Marks parameters in the Diagram=>X/Y/Z-Axis=>Parameters dialog box.

If you have 100 to 200 fairly evenly distributed data points, you will produce an accurate contour map with a grid composed of 30 * 30 points. Details on the contour map can be lost if grid density is set too low. Resolution depends on the distribution of the data points in the x/y coordinate plane.

Type
You have a choice between linear and non-linear interpolation with this option. If you want to plot beyond the data hull, you should choose the Thin-Plate-Spline method.
Smoothing
Interpolated data can be smoothed by entering a number between 1 and 5 in the Factor edit field. For minimal smoothing enter 1, for maximum smoothing enter 5.

Comment

When you change any settings in the dialog box, the plot will be recalculated. This means the positions of the interactively inserted isoline labels in the 2D Plot will be lost.

For some datasets the Thin-Plate-Spline interpolation fails. In this case a linear interpolation is executed and a warning is displayed in the event window.

id-1029555