BUCHI NIRCal User Manual
Page 42
NIRCal 5.5 Software Manual
42
NIRCal 5.5 Manual, Version A
A reduction of the dimensions is performed when the number of PC's (i) is not higher than 1.501.
Through this type of data reduction it is impossible to lose information.
With today's powerful computers, the prime object is no longer the reduction of the data volume.
Today, the main goal of PCA is to find and automatically evaluate characteristics of identity, quality
and quantity in the spectra.
As a result of the PCA, the following is obtained:
Mean spectrum:
Calculated by averaging the intensity values at each wavelength. The centre of the new
coordinate system is shifted to that point: mean centering.
Formula:
Principal Components: U
i
(k)
New space directions in the point cluster, which are also called principal components. PCs are
artificial differential spectra.
Each calibration can have i PCs (default is: 15).
The mean spectrum and PCs are always fixed for the calibration.