In Origin, contour plots can be created using one of Origin's several matrix conversion and gridding algorithms, or by direct plotting of XYZ worksheet data. For a discussion of contouring algorithms, see the algorithm page for contour plot. Note that prior to Origin 2016, xyz (worksheet data) were normalized before contours were generated; Beginning with Origin 2016, raw x and y data values are used. See Normalize Data for XYZ Contour/Surface Plot.
When worksheet data are plotted directly (without gridding), the contour plot's Details dialog box will display an extra tab -- the Contouring Info tab (note that these controls also apply to theta-r contour plots).
The Boundary controls allow you to mask the edges of the XYZ contour plot. There are three choices:
The raw data boundary. It also can be affected by Smoothing parameters.
The layer frame determined by Origin extrapolation.
Customize a new boundary by setting Boundary X Data, Boundary Y Data (and Boundary Z Data).
Prior to Origin 2018 SR0, the application of a custom boundary sometimes generated an imperfect fill at boundary margins. This has been improved in 2018. The user can restore the previous contour-fill behavior using system variable @TCSM.
Perform XYZ interpolation to smooth the contour plot using Thin Plate Spline (TPS) algorithm
It provides controls as below.
Expand the number of plotted points by multiplying the original number of points by this factor. This number should not be less than 1.
The Thin Plate Spline smoothing parameter. Determines the degree of smoothing. Smaller numbers produce less smoothing.
For Origin 2017 and any ealier versions, once you selected Custom Boundary radio box, the Smoothing check box will be checked and grayed out by default. You are not allowed to turn the smoothing off any more.
However, sometimes you will find the color scale and color levels are changed after applying the custom boundary. To prevent it, you will need to use the system variable @TCS to set the maximum number of data points for tri-contour smoothing as small as possible, for example @tcs=0, to "turn off" the smoothing visually.
When the contour plot is a polar contour plot, this tab is enabled.