Studing structure in LOCAL for validation

One way to understand the structure of the spectra population is to order the database of spectra by the constituent of interest and select different groups (in this case eight). One group is keeping it for validation and the others for calibration, so in the case of the figure I use “group_6” for validation and all the rest for calibration.

I continue with all possible combinations.

 It is the same that “cross validation”, but in this case I use the LOCAL algorithm. The resulting statistics (RSQ , SEP, ….), help me to understand if the calibration will perform as it should in routine and to fine outliers.

It was very useful to improve the performance of a calibration for Process Analysis, where GLOBAL, did not perform well, and LOCAL seems to be better.

In Process we can´t expect very nice statistics, but not so high RSQ can help you to see tendencies, and take decisions immediately.