Metrohm Vision Manual - Manual (Page 136)

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Equation editing
Vision selects the wavelength or wavelengths so that the maximum correlation is obtained. The last
active wavelength is shown by the gray bar on the upper display. This wavelength can be changed by
dragging the bar to the desired wavelength position, or by clicking on Regression/Edit Wavelength
and typing in the value.
To add a new wavelength to the equation by clicking on Regression/Add Term. The equation
parameters, statistics, and graphs are recalculated and views updated.
The last wavelength can be removed from the MLR equation by clicking on Regression/Rollback
Term. The equation parameters, statistics, and graphs are recalculated and views updated.
To move spectra between calibration, validation, and outlier sets, right click on a dot representing a
spectrum in any plot or the spectrum name in the equation tree. Vision will reset the MLR equation
to the first term. The equation parameters, statistics, and graphs are recalculated and views updated.
To change the control chart options, click on View/Control Chart Parameters.
To save the equation, click on Regression/Save Equation. To save the equation under a different
name, click on Regression/Save Equation As.
5.4.2 Partial Least Squares
Partial Least Squares (PLS) regression allows a user to use the spectral information of a whole range
of wavelengths, even the full spectrum. This method eliminates colinearity (high correlation between
wavelength terms) that are difficult to overcome with classical methods.
Preparation
1. Click on Mode/Quantitative Analysis/Regression to enter the calibration development
program. The last active project will be opened. Expand the product for which you want to
create the equation. The product should have the calibration set saved in the sample selection
program.
2. Select the proper equation by double-clicking on it. The equation icon will turn blue.
Configuring the Method
1. Click on Regression/Edit Regression Method.