Variable Importance in NIR "PLS" Models (CARET)

This is a function of the R Caret package to check the importance of the variables in a regression. In the case of the model developed with the sunflower seed to determine oleic acid (model_oleic), we can plot it and check which variables have more importance and this is done with a simple step:

 

varImp_pls<-varImp(model_oleic)

 

And the best way to check it is plotting the results as a spectrum:

 

matplot(wavelengths,varImp_pls$importance,type="l",
        xlab="wavelengths",
        ylab="importance",
        ylim =c(min(varImp_pls$importance)-0.1,
                max(varImp_pls$importance)+0.1),
        col="blue")

 

To obtain this spectra:

We can see that the zone of 1700 to 1800 has higher important than the rest due to the peaks linked to the "oil" around 1720 and 1760 nm.