The model, as represented by B-vector of regression
coefficients, showed strong oscillatory behaviour across the spectral range
with numerous spikes above 950 nm. A persistent spiky sequence in a B-vector
regression coefficient display normally indicates over-fitting of the data.
This supports the contention that the
PLS models are using too many latent variables. The largest regression
coefficient occurred at 914 nm. This is consistent with the presence of the
third overtone of the carbohydrate CH absorbance band that nominally occurs in
the 900-920 nm range (Williams and Norris, 1981). This absorbance band for DM
and/or sugar determination as it is removed from troublesome interferences from
the water absorbance bands that typically dominate spectra of fruit.
P. 303-304 in Clark et al., (2003) Dry matter determination
in Hass avocado by NIR spectroscopy, Post Biol and Tech, 29, 300-307
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