It is clear that we can discriminate between olive oil and sunflower oil, but let´s see the reason for the sub-clusters in the sunflower oil.
Samples sflw6da, sflw7da, sflw8da, sflw9da, sflw10da are refined sunflower, so it is filtered and processed, that means differences in the water content, and some other physical properties, but apart from that these samples have a similar spectra to samples sflw2da, sflw3da, sflw4da and sflw5da, and the reason is that the content of oleic acid is similar.
Samples sflw11da, sflw12da and sflw13da have a higher value of oleic acid, so the 2140 absorption band is lower respect to the others and there is a shift of the peak position around 1720 nm to a higher wavelength . These points allow to discriminate these samples respect to sflw6da, sflw7da, sflw8da, and these points plus the water content and other physical changes makes also possible the discrimination respect to sflw6da, sflw7da, sflw8da, sflw9da, sflw10da.
See if interested: previous posts:
Looking to the spectra (sunflower oil)
Hierarchical Cluster Analysis (ChemoSpec) - 01
Hierarchical Cluster Analysis (ChemoSpec) - 02 (interesting comment from Bryan Hanson)