Notes on finding mineralogy with Interesting Features Finder + Spectral Angle Mapper

Interesting Features Finder(IFF) Wu, Q. et al. (2022) ‘Interesting features finder (IFF): Another way to explore spectroscopic imaging data sets giving minor compounds and traces a chance to express themselves’, Spectrochimica Acta Part B: Atomic Spectroscopy, 195, p. 106508. Available at: https://doi.org/10.1016/j.sab.2022.106508. is a new method to find the archetypal spectra among a dataset so all other spectra in the dataset is then a linear combination of these so called interesting spectra. In rocks these interesting spectra often correspond to the minerals in the dataset which is exactly what we want.

Mathematically it tries to approximate the extreme points of a convex hull Check the wikipedia page https://en.wikipedia.org/wiki/Convex_hull to understand it mathematically. We would like to put all the spectra in 8188-dimensional space as vectors and put a rubber band around them and pick the ones that the rubber band touches. Calculating the true convex hull is computationally unfeasible. IFF is one method to approximate it that works with our spectral data nicely. of the spectra. There's good arguments that finding a convex hull is in a sense the optimal solution to chemometrics problems.

Example 1: Find minerals on piece of drill core with IFF and map them with SAM

We have a piece of drill core(=a rock) imaged with LIBS. If we run IFF for this data