The regression method
assumes that systemic variations observed in the spectra are
a consequence of the concentration change of curcuminoid
in the sample. The spectral matrix and data matrix are
broken into their eigenvectors, which are called factors or
principal components. The advantage of this approach is
that not all of the principal components are necessary to
describe. Only the relevant principal components will then
be used instead of the original spectral data and then system
is analyzed for each component spectra to identify