Peak Analyzer, ALS Baseline


This page is added to the wizard when Baseline Mode is set to Asymmetric Least Squares smoothing (ALS).

PA ALS Page.png
  • Menu Command: Analysis: Peaks and Baseline: Peak Analyzer: Open Dialog
  • Window Types: Workbook, Graph

Dialog Theme

Dialog Theme See Peak Analyzer Themes.

Settings

Specify parameters for Asymmetric Least Squares Smoothing (ALS) method.

Asymmetric Factor [0-1] Specify weight of points above the baseline in each iteration. For positive peaks it should be close to 0, and close to 1 for negative peaks. The asymmetric factor must be between 0 and 1. The smaller the asymmetric factor is, the less effect points above the baseline have on baseline in next iteration. The asymmetric factor should be chosen close to 0 for positive peaks, eg., 0.001, and close to 1 for positive peaks, eg.,0.99
Threshold (%) Specify the threshold to determine points above the baseline (for positive peaks) or below the baseline (for negative peaks). The threshold is defined by the ratio of a critical distance of point to baseline to that of peak to baseline. A point whose distance to baseline is greater than the threshold will be considered above the baseline (for positive peaks). And the threshold must be between 0 and 1 (not equal to 1).

The smaller the threshold is, the more points above the baseline (for positive peaks) will be excluded to determine the baseline in next iteration.
Smoothing Factor Specify the smoothness of the baseline. The smoothing factor must be greater than 0, and the typical value is 2 and 9. The larger the smoothing factor is, the smoother the baseline will be.
Number of Iterations Specify number of iterations. The typical value is 10. In each iteration, it will find a baseline, and determine which points will be considered as points above the baseline for next iteration.
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