Fit Line to Profile
Description
This Step is used to fit a line to the input profile and measure the deviations from the fitted line.
Workflow
The process of configuring this Step is shown below.
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Configure the input. Connect the ports manually or select the input(s) under Input in the parameter configuration panel.
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Set the feature region mode.
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Set the region for line fitting.
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Select the desired output(s) under Output. For an expandable output item, click ▶ and configure the Min and Max values of the acceptable range.
Parameter Description
- Feature Region Mode
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This parameter determines whether the region for fitting and the region for measurement are the same.
Options: None, Combined, Separated
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Combined: The fitting region and measurement region are the same.
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Separated: The fitting region and measurement region are different.
Default setting: Combined
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- Fitting Method
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This parameter specifies the method of fitting the line to the profile.
Options: Simple, Robust
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Simple: High speed, but low accuracy.
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Robust: Low speed, but high accuracy.
Default setting: Simple
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- Outlier Fraction
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This parameter defines the proportion of outliers to be removed during line fitting, thus resulting in a better result. It will be displayed when Fitting Method is set to Robust.
Default setting: 30.000%
- Measurements Percentage
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This parameter specifies percentile of the nearest point to the line that is referenced when calculating the error in fitting the line.
Default setting: 50.000%
In statistics, percentiles are found by taking a large set of numerical data, arranging it in ascending order, and then dividing it into 100 groups with an equal number of data points. Each of the 99 dividing points is called a percentile of the data set.
Output Description
Select the output item(s) according to the actual measurement requirements. Then the corresponding data will be output after the Step is run.
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If you select an expandable output item, you must expand it by clicking ▶, and then set the Min and Max values to determine the acceptable range. If the output value falls within the acceptable range, the measurement item is judged as passing (OK), or else it is judged as failing (NG). |
| Output Item | Description |
|---|---|
Standard Deviation |
The standard deviation of the data points with respect to the fitted line. |
Min Error |
The minimum error of the data points from the fitted line. |
Max Error |
The maximum error of the data points from the fitted line. |
Error at Percentile |
The maximum error from points within Measurements Percentage to the fitted line. |
Offset |
The Z value of the intersection of the fitted line with the Z-axis. |
Angle |
The angle of the fitted line with respect to the X-axis. |
Min Error X |
The X value of the point with the minimum error. |
Min Error Z |
The Z value of the point with the minimum error. |
Max Error X |
The X value of the point with the maximum error. |
Max Error Z |
The Z value of the point with the maximum error. |
Arithmetic Mean |
The mean of the distances from the data points to the fitted line. |
Error Range |
The range of error of the data points from the fitted line. |
Fitted Line |
The fitted line obtained. |
Troubleshooting
Invalid Parameter
| No. | Error | Error Description | Possible Causes | Solution |
|---|---|---|---|---|
1 |
Inappropriate outlier fraction |
When Fitting Method is set to Robust, Outlier Fraction is not set properly. |
The set outlier fraction is not within [0, 1]. |
Reset Outlier Fraction to ensure that the value is within [0, 1]. |
2 |
Inappropriate measurements percentage |
Measurements Percentage is not set properly. |
The set measurements percentage is not within [0, 1]. |
Reset Measurements Percentage to ensure that the value is within [0, 1]. |
Invalid Feature Region
| No. | Error | Error Description | Possible Causes | Solution |
|---|---|---|---|---|
1 |
Insufficient data points in the region for measurement |
There are not enough points in the measurement region for the measurement to be completed. |
Data points are not included in the region for measurement. |
Check and adjust the region for measurement to ensure that data points are included. |
2 |
Insufficient data points in the region for line fitting |
There are not enough points in the fitting region for the fitting to be completed. |
The number of points in the region for line fitting is less than 2. |
Check and adjust the region for line fitting to ensure that the number of points in it is no less than 2. |