Create and returns a function to estimate hc and clustered standard errors for panel data.
get_robust_vcxt_panel(func_name)
A function.
A character.
Croissant, Y., Millo, G. (2017). "Robust Standard Error Estimators for Panel Models: A Unifying Approach." Journal of Statistical Software, 27(2), 1-43. tools:::Rd_expr_doi("10.18637/jss.v082.i03").