BUCHI NIRCal - Manual (Page 124)

NIRCal 5.5 Software Manual
124 NIRCal 5.5 Manual, Version A
Calculation
Data Description [%]
To determine the number of primary PCs with a certain Data description
(in %).
Available for Cluster and PCR Method only.
Num Primary PCs Change the value at Num Primary PCs to the number defined by the
graphic “
X-PRESS ”. The limit of maximum number PCs is number of C-
Set spectra.
Advanced
Mean centering after
Pretreatments
Sets the Mean Centering after finishing Pretreatments ON or OFF.
All implemented algorithms (PCA, PCR, PLS) prefer a mean
centering of the data.
In very special situation it is possible to try the calibration without mean
centering (e.g. SIMCA).
Max. Iterations The maximum number of iterations for the internal PCA, PCR and PLS
algorithm.
When the maximum iterations are reached the algorithm will stop the
calculation at the actual PC. All the following calculations will be done
with this actual number of PCs instead the desired number of primary
PCs.
Tip: for very difficult data set, set the number of iterations up to 3'000.
NOTE: Max. iteration limit is the number of C-Set spectra.
3.8 Secondary PCs
3.8.1 Secondary PCs for qualitative Calibration
The secondary / calibration principal components are responsible for the separation of the different
substances and are used for the tolerance radii calculation. Several graphics or tables can help
decide which principal components will lead to a successful separation of the properties.
The most comprehensive results are in the Menubar: View / Overview.