data pca
http://www.sthda.com/english/articles/31-principal-component-methods-in-r-practical-guide/119-pca-in-r-using-ade4-quick-scripts/
https://academic.oup.com/bioinformatics/article/17/9/763/206456


korespondenční

http://setosa.io/ev/principal-component-analysis/