Principal Nested Spheres for dimension reduction of directional and pre-shapes
I recommend using itype = 9.
The analysis of PNS is proposed in
- Sungkyu Jung, Ian L. Dryden and J. S. Marron (2012). “Analysis of Principal Nested Spheres”, Biometrika, 99(3), 551-568.
The new testing procedure (testing to determine whether to use the great sphere or a smalle sphere) is based on
- Byungwon Kim, Joern Schulz and Sungkyu Jung (2020). “Kurtosis test of modality for rotationally symmetric distributions on hyperspheres”, The Journal of Multivariate Analysis, 178, Article 104603.