BUCHI NIRCal - Manual (Page 120)

NIRCal 5.5 Software Manual
120 NIRCal 5.5 Manual, Version A
Gap2 Derivatives Linear Filter Coefficients
First Derivative BCAP Gap2
(db1g2) 1,0,0,1,0,0,0,0,0,-1,0,0,-1, 4
First Derivative Taylor 3
Points Gap2 (dt1g2) 1,0,0,0,0,0,-1, 2
First Derivative Savitzky-
Golay 9 Points Gap2
(dg1g2) -86,0,0,142,0,0,193,0,0,126,0,0,0,0,0,-126,0,0,-193,0,0,-
142,0,0,86, 1188
Second Derivative BCAP
Gap2 (db2g2) 1,0,0,-2,0,0,1, 2
Second Derivative Taylor 3
Points Gap2 (dt2g2) 1,0,0,-2,0,0,1, 2 *)
Second Derivative Savitzky-
Golay 9 Points Gap2
(dg2g2) 28,0,0,7,0,0,-8,0,0,-17,0,0,-20,0,0,-17,0,0,-
8,0,0,7,0,0,28,462
Second Taylor 3 Points
(Segment5 Gap5)
Gap2 (ds2g2) 1,0,0,1,0,0,1,0,0,1,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,-
2,0,0,-2,0,0,-2,0,0,-2,0,0,-
2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,0,0,1,0,0,1,0,0,1,0,0,1,
5
Third Derivative Taylor 5
Points Gap2 (dt3g2) 1,0,0,-2,0,0,0,0,0,2,0,0,-1, 2
Gap2 Smoothing
Linear Filter Coefficients
Average 3 Points Gap2
(sa3g2) 1,0,0,1,0,0,1,3
Average 9 Points Gap2
(sa9g2) 1,0,0,1,0,0,1,0,0,1,0,0,1,0,0,1,0,0,1,0,0,1,0,0,1,9
Savitzky-Golay 9 Points Gap2
(sg9g2) -
21,0,0,14,0,0,39,0,0,54,0,0,59,0,0,54,0,0,39,0,0,14,0,0,-
21, 231
3.6 Primary PCs
Primary PCs are used for the reconstruction of measured and pretreated spectra. The optimum
number of primary PCs will be achieved if the spectra are described down to the limit of noise of the
spectrometer. Primary PCs influence the spectra reconstruction and therefore are responsible for the
residuum spectra and the residual.
The more primary PCs are used, the smaller the allowed residual of the calibration. If too many
primary PCs are selected, a calibration is overfitted. In this situation only the calibration spectra
will be identified correctly but not necessarily spectra of additional validation samples represented in
the project.
If too few primary PCs are selected, the calibration might not be selective enough for the
products (underfitted).
Tools for the selection of the optimal number of primary PCs:
The X-PRESS function shows from which PCs on, an additional PC does not improve the
reconstruction of the spectra. The smallest number of PCs that still shows changes should be
selected.
The Loadings / PCs themselves can be judged. PCs that appear noisy should not be used.
The Residuum spectra can be checked. The amplitude of these spectra with the selected
number of primary PCs should be about the same.