Operators

regress_contours_xld (Operator)

Name

regress_contours_xld — Calculate the parameters of a regression line to an XLD contour.

Signature

regress_contours_xld(Contours : RegressContours : Mode, Iterations : )

Description

regress_contours_xld calculates the following parameters for the input XLD contours Contours, and stores them with the resulting contours as global attributes:

• the coordinates of the normal vector of the regression line, i.e., the least-squares approximating line, of all contour points; the normal vector always points from the origin to the line (attributes: 'regr_norm_row', 'regr_norm_col'),

• the mean of the Euclidian distance of the contour points from the regression line (attribute: 'regr_mean_dist'),

• the standard deviation of these distances to the regression line (attribute: 'regr_dev_dist').

For Mode = 'no', the parameters of the regression line are calculated for all points of the contour. In addition, three different kinds of outlier treatment can be applied. Outliers are contour points which do not lie on the general contour direction in an “obvious” manner, and thus “distort” the resulting regression line.

Mode =

• 'drop': All contour points further away from the contour than the mean distance to the regression line are ignored for the calculation of the undistorted regression line.

• 'gauss': The distances of the contour points are weighted according to their probability of occurrence in a Gaussian distribution around the normal regression line.

• 'median': Here, also a normal distribution is assumed for the distances to the normal regression line, however with the outlier-independent standard deviation {median(all dist.)}over(0.6745). Again, the distances are weighted, and points further away than a certain distance are ignored for the undistorted regression line.

The calculation of the undistorted regression line can be iterated several times (Iterations).

Parallelization

• Multithreading type: reentrant (runs in parallel with non-exclusive operators).
• Multithreading scope: global (may be called from any thread).
• Processed without parallelization.

Parameters

Contours (input_object)  xld_cont-array object

Input XLD contours.

RegressContours (output_object)  xld_cont-array object

Resulting XLD contours.

Mode (input_control)  string (string)

Type of outlier treatment.

Default value: 'no'

List of values: 'drop', 'gauss', 'median', 'no'

Iterations (input_control)  integer (integer)

Number of iterations for the outlier treatment.

Default value: 1

Suggested values: 1, 2, 3, 5, 10, 20