To check the multicollinearity, the method I know is to use vif
in car
library. To use vif
, we first have to fit a model. However, the data is $p > n$. We cannot fit a linear regression model with OLS. Then we try to fit in LASSO but all coefficients are 0. Hence, I cannot check the multicollinearity.
Is there a way to check multicollinearity without a model? For example, correlation matrix. But what if $x1 = x2 + x3$?
I have read this postpost . I am not clear how does PCA detect (rather than handling) multicollinearity.