Trying to find high content gypsum samples (part 3)

 If we go back to the post: "PCA with the first derivative" we saw how there was some groupings (in the PC2 vs. the rest PC maps) in the scores, after, when looking to second loading we though that could be the samples with gypsum content. 

In the last two posts : "Trying to find high content gypsum samples (part 1)" and "Trying to find high content gypsum samples (part 2)",  we found those samples by correlation with a Gypsum reference spectra, and now we can create a new variable called "gypsum" which takes the factor value "Yes" or  "No", so now we can see easier in the score maps if that grouping was due to the content of gypsum:

pairs(scores_1df[ ,1:6], col = scores_1df$gypsum)