Regenerated spectra

Figure 60 also contains a plot of the differences between the original and the regenerated spectra. This is identical to the residuals. The residuals of... 

Figure 61. Plot of the residuals of the all the regenerated spectra in the two training sets, A1 and A2.

Figure 62. Plots (left column) of a regenerated spectrum ( — ) and the original spectrum ( ) of a sample from each of the 3 validation sets A3, A4, and A5. Residuals for all of the regenerated spectra in each of the 3 validation sets are also shown (right column).

So there is no way that the basis vectors for the Al spectra can span all of the variance added to the A5 spectra by that component. Thus, it makes sense that major spectral features are missing from the regenerated spectra and show up, instead, in the residuals. 

PCA factors from A1 regenerate spectra for A1 PCA factors from A1 regenerate spectra for A3 PCA factors from A1 regenerate spectra for A4 PCA factors from A1 regenerate spectra for AS... 

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