Strategies for EELS Data Analysis. Introducing UMAP and HDBSCAN for Dimensionality Reduction and Clustering

Hierarchical density-based spatial clustering of applications with noise (HDBSCAN) and uniform manifold approximation and projection (UMAP), two new state-of-the-art algorithms for clustering analysis, and dimensionality reduction, respectively, are proposed for the segmentation of core-loss electron energy loss spectroscopy (EELS) spectrum images. The performances of UMAP and HDBSCAN are systematically compared to the other clustering analysis approaches used in EELS in the literature using a known synthetic dataset. Better results are found for these new approaches. Furthermore, UMAP and HDBSCAN are showcased in a real experimental dataset from a core-shell nanoparticle of iron and manganese oxides, as well as the triple combination non-negative matrix factorization-UMAP-HDBSCAN. The results obtained indicate how the complementary use of different combinations may be beneficial in a real-case scenario to attain a complete picture, as different algorithms highlight different aspects of the dataset studied.

Automated summary

In this study, two new clustering analysis methods and dimensionality reduction methods (HDBSCAN and UMAP) were proposed for the segmentation of core-loss electron energy loss spectroscopy (EELS) spectrum images. The performances of HDBSCAN and UMAP were systematically compared to other methods using synthetic and experimental datasets, and better results were obtained. The results also showed that the combination of different algorithms can provide a more comprehensive understanding of the dataset studied.