9.5.1.2 The (Plot Details) Contouring Info Tab

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).

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General Contouring Info tab	General Contouring Info tab for Ternary Contour graph

1 Boundary
2 Smoothing
3 Interpolate in Polar Coordinates

Boundary

The Boundary controls allow you to mask the edges of the XYZ contour plot. There are three choices:

Data Boundary

The raw data boundary. It also can be affected by Smoothing parameters.

Layer Boundary

The layer frame determined by Origin extrapolation.

Note:

When layer boundary is selected, the space between data and boundary is filled by extrapolation. In this case the Smoothing Parameter must be set.
The maximum number of data points for tri-contour smoothing is controlled by system variable @TCS. Its default value is 4000, beyond which no smoothing will be done. So if the number of points in the contour is greater than 4000, layer boundary is not recommended.

Custom Boundary

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.

Smoothing

Perform XYZ interpolation to smooth the contour plot using Thin Plate Spline (TPS) algorithm

It provides controls as below.

Total points increase factor	Expand the number of plotted points by multiplying the original number of points by this factor. This number should not be less than 1.
Smoothing Parameter	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.