Mcu. Araujo et al., The successive projections algorithm for variable selection in spectroscopic multicomponent analysis, CHEM INTELL, 57(2), 2001, pp. 65-73
The "Successive Projections Algorithm", a forward selection method which us
es simple operations in a vector space to minimize variable collinearity, i
s proposed as a novel variable selection strategy for multivariate calibrat
ion. The algorithm was applied to UV-VIS spectrophotometric data for simult
aneous analysis of complexes of Co2+ ,Cu2+, Mn2+, Ni2+ e Zn2+ with 4-(2-pir
idilazo)resorcinol in samples containing the analytes in the 0.02-0.5 mg 1(
-1) concentration range. A convenient spectral window was first chosen by a
procedure also proposed here and applying Successive Projections Algorithm
to this range allowed an improvement of the predictive capabilities of Pri
ncipal Component Regression, Partial Least Squares and Multiple Linear Regr
ession models using only 20% of the number of wavelengths. Successive Proje
ctions Algorithm selection resulted in a root mean square error of predicti
on at the test set of 0.02 mg l(-1), while the best and worst realizations
of a genetic algorithm used for comparison yielded 0.01 and 0.03 mg l(-1).
However, genetic algorithm took 200 times longer than Successive Projection
s Algorithm, and this ratio tends to increase dramatically with the number
of wavelengths employed. Finally, unlike genetic algorithm, Successive Proj
ections Algorithm is a deterministic search technique whose results are rep
roducible and it is more robust with respect to the choice of the validatio
n set. (C) 2001 Elsevier Science B.V. All rights reserved.