A case study of extrapolation in NIR modelling — A chemometric challenge at ‘Chimiométrie 2009’

Since 2004, a challenge is proposed at the “Chimiométrie” conference organized by the GFC (“Groupe Français de Chimiométrie”). The annual congress was held in Paris 30 November and 1 December 2009. The data are still available on the GFC website (www.chimiometrie.org/). The data for this session were extracted from the CRA-W (Walloon Agricultural Research Centre, www.cra.wallonie.be/) spectral data base. The calibration set and the validation set (the reference values for the latter were not available to the participants) were set up to have an obvious case of extrapolation. The data sets were from whole rapeseed samples and the parameter to be calibrated was the total glucosinolate content. Seven participants reported results and, according to the highest R2 of prediction, three were asked to present their approach during the conference. These approaches and the ones of the challenge organizers are presented in this paper.