BUCHI NIRCal User Manual
Page 121
Chemometrics
NIRCal 5.5 Manual, Version A
121
In this example, 3 primary PCs are necessary, each loading contains spectral information. PCs 4 to 10
are very small and have only noise with no useful information.
Check the number of primary PCs with the help of the graphic
X-PRESS
(in the Overview, or open the
graphic in the Menubar : Graphics / X-PRESS) and Loading.
Additional tool:
The Eigenvalue of the PCs may provide information of the information content of the PCs. The
reliability of the Eigenvalue is dependent on the applied data pretreatment.
The selected number of primary PCs should be adjusted and the calibration recalculated.
The more primary PCs are used, the smaller the allowed residual of the calibration.
If the primary PCs are selected correctly, the residuum spectra are similar for the C- and V-
Set.
Example of correct primary PC selection: