BUCHI NIRCal - Manual (Page 47)

Chemometrics
NIRCal 5.5 Manual, Version A 47
Additional tool:

The Score Disorder values show how effectively a particular PC separates different properties
(substances) from each other. By scanning the score values in one direction of a PC and
counting the changes between the membership of A or B the disorder value is achieved. If a
PC completely separates all calibration properties, the disorder values is the [number of
calibration properties - 1]. PCs with small disorder values are possible calibration PCs.
The selected number of secondary PCs should be adjusted and the calibration should be recalculated.
Link:
Secondary PCs
The tolerance ring radii are determined according to the secondary PCs.
For this calculation the smallest possible rectangle (rectangle in 2D, a cuboid in 3D, an n-
dimensional cuboid in n-dimensions) constructed around each C-Set. The sides of the rectangles (a
and b) are parallel to the axis of the PCs. The distance from the center to the side of the smallest
possible rectangle is a measure of the extension of the C-
Set, this is the so called “Property Box
Radii ”. A ‘virtual rectangle’ is created 5 times greater than the rectangle around the C-Set.
The following distances will be calculated:

R1 smallest distance between a spectrum (substance B) to the closest spectrum of a different
property (substance A).

R2 smallest distance between a spectrum (substance B) to the side of its virtual rectangle.

R3 smallest distance between a spectrum (substance B) to the closest spectrum of its own
property (substance B).

R4 mean value out of all R3 distances of the same property.
With these distances it is possible to calculate tolerance circles with a radius r for every calibration
spectra by using Formula 1, 2 or 3.
Formula 1:
Min. of r = R1/2 * f
or r = (R1+R2)/4 * f
The smaller of the two possible values for the radius “r” is used. The default setting for the Radii Blow
Up factor "f" is 1.
Depending on the extension of the cluster (R2) and the distance between the two closest clusters
(R1), the circles are closer or further away from each other. With a Radii Blow Up of 1 two circles can
just touch each other but do not overlap.
For chemically different substances the Radii Blow up (f) may be reduced (0< f <1) in order to
increase the sensitivity of the calibration.
NOTE: It is not suggested to have a Radii Blow up (f) higher than 1: it can cause overlapping rings!