How to plot marginal effect of an interaction after felm() function
问题 I ran a regression based on a "giant" panel data with a bunch of unit fixed effects. So I employed function "felm()" from package "lfe". In addition, I have an interaction term of two continuous variables in the regression. But when plotting how the marginal effects of x on y vary with x2, it seems that the objects produced by "felm()" are often incompatible to most plotting functions like "ggplot", "interplot()" and "meplot". But I have to use "felm()" because I need to control for a large