BUCHI NIRCal - Manual (Page 46)

NIRCal 5.5 Software Manual
46 NIRCal 5.5 Manual, Version A
The Büchi NIRCal software package only works with the normalised distances, the user can not see
the result without it.
3.1.2 Cluster: CLU
Goal: to identify different chemical substances using the PCA and as a result to get a well separated
cluster area in the scores plot for each substance.
The clusters are created according the selected secondary PCs. Secondary PCs are that PCs among
the primary PCs, which shows a clear separation of the substances and the scores are good
repeatable. These secondary PCs are responsible and used for the tolerance radii calculation.
Tools for the selection of secondary PC's:

the scores of the spectra will be shown dependent to the PCs: Scores against Spectra. The
scores of all spectra of each substance should be close together, but separated from the
scores of all other substances;

the Property Box Radii plot shows the repeatability [(max-min) scores / 2] of the scores for
each property. PCs showing small Property Box Radii values (normally below 0.1) are
important for the calibration;

2 and 3 dimensional score plots: PCs having repeatable scores should be selected.