13.6 Polychoric correlation, PCA

• The psych package has a bunch of stuff for dealing with categorical variables (common in psych data). https://cran.r-project.org/web/packages/psych/psych.pdf. It looks like

• fa using the option cor=“poly” will do factor analysis with polychoric correlations.

• principal using cor="poly" will do PCA with polychoric correlations

Random other resources:

• https://medium.com/geekculture/everything-about-principal-component-analysis-3c7aed41e1f9#:~:text=Polychoric%20Correlation%20%2F%20PCA,-Polychoric%20correlation%20measures&text=Information%20about%20each%20unobserved%20variable,Olsson%201979%3B%20Drasgow%201986).