Species abundance data can be preprocessed with Hellinger transformation or chord transformation data before PCA analysis. Because the Hellinger distance or chord distance with-without data is equal to \(\sqrt2\sqrt{1-Ochiai\ similarity}\), therefore, the sorting diagram (type 1 scale) of PCA analysis after Hellinger transformation or chord transformation with-without data is internal sample The distance between the squares is the Ochiai distance. \(\sqrt2\sqrt{1-Ochiai\ similarity}\) is a distance measure, which is also suitable for the analysis of species data. The processed data is then used for pca without norm.