This is the second derivative spectra of the raw spectra we have sawn in the post: “Hierarchical Cluster Analysis (ChemoSpec) – 01”. In that post we saw some clusters, but the distance between the clusters was not high, so it was clear that some math treatment should be applied to remove baseline shifts and to increase the differences between the clusters as much as possible.

Well, let’s see now the HCA in this case:

Well, now it looks much better, Olive samples in one cluster, and sunflower oil samples in another. We can see also two sub-cluster in the sunflower samples. Looking to the spectra we can see some reasons for that more clearly now. That will be treated in the next post.